blocks|key|595967|text|public+static+bool+IsValidGtin(string+code)
{
++++if+(code+!=+(new+Regex("[%5E0-9]")).Replace(code,+""))
++++{
++++++++//+is+not+numeric
++++++++return+false;
++++}
++++//+pad+with+zeros+to+lengthen+to+14+digits
++++switch+(code.Length)
++++{
++++++++case+8:
++++++++++++code+=+"000000"+%2B+code;
++++++++++++break;
++++++++case+12:
++++++++++++code+=+"00"+%2B+code;
++++++++++++break;
++++++++case+13:
++++++++++++code+=+"0"+%2B+code;
++++++++++++break;
++++++++case+14:
++++++++++++break;
++++++++default:
++++++++++++//+wrong+number+of+digits
++++++++++++return+false;
++++}
++++//+calculate+check+digit
++++int[]+a+=+new+int[13];
++++a[0]+=+int.Parse(code[0].ToString())+*+3;
++++a[1]+=+int.Parse(code[1].ToString());
++++a[2]+=+int.Parse(code[2].ToString())+*+3;
++++a[3]+=+int.Parse(code[3].ToString());
++++a[4]+=+int.Parse(code[4].ToString())+*+3;
++++a[5]+=+int.Parse(code[5].ToString());
++++a[6]+=+int.Parse(code[6].ToString())+*+3;
++++a[7]+=+int.Parse(code[7].ToString());
++++a[8]+=+int.Parse(code[8].ToString())+*+3;
++++a[9]+=+int.Parse(code[9].ToString());
++++a[10]+=+int.Parse(code[10].ToString())+*+3;
++++a[11]+=+int.Parse(code[11].ToString());
++++a[12]+=+int.Parse(code[12].ToString())+*+3;
++++int+sum+=+a[0]+%2B+a[1]+%2B+a[2]+%2B+a[3]+%2B+a[4]+%2B+a[5]+%2B+a[6]+%2B+a[7]+%2B+a[8]+%2B+a[9]+%2B+a[10]+%2B+a[11]+%2B+a[12];
++++int+check+=+(10+-+(sum+%25+10))+%25+10;
++++//+evaluate+check+digit
++++int+last+=+int.Parse(code[13].ToString());
++++return+check+==+last;
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|595968|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>public static bool IsValidGtin(string code)
{
 if (code != (new Regex("[^0-9]")).Replace(code, ""))
 {
 // is not numeric
 return false;
 }
 // pad with zeros to lengthen to 14 digits
 switch (code.Length)
 {
 case 8:
 code = "000000" + code;
 break;
 case 12:
 code = "00" + code;
 break;
 case 13:
 code = "0" + code;
 break;
 case 14:
 break;
 default:
 // wrong number of digits
 return false;
 }
 // calculate check digit
 int[] a = new int[13];
 a[0] = int.Parse(code[0].ToString()) * 3;
 a[1] = int.Parse(code[1].ToString());
 a[2] = int.Parse(code[2].ToString()) * 3;
 a[3] = int.Parse(code[3].ToString());
 a[4] = int.Parse(code[4].ToString()) * 3;
 a[5] = int.Parse(code[5].ToString());
 a[6] = int.Parse(code[6].ToString()) * 3;
 a[7] = int.Parse(code[7].ToString());
 a[8] = int.Parse(code[8].ToString()) * 3;
 a[9] = int.Parse(code[9].ToString());
 a[10] = int.Parse(code[10].ToString()) * 3;
 a[11] = int.Parse(code[11].ToString());
 a[12] = int.Parse(code[12].ToString()) * 3;
 int sum = a[0] + a[1] + a[2] + a[3] + a[4] + a[5] + a[6] + a[7] + a[8] + a[9] + a[10] + a[11] + a[12];
 int check = (10 - (sum % 10)) % 10;
 // evaluate check digit
 int last = int.Parse(code[13].ToString());
 return check == last;
}
</code></pre>

blocks|key|595978|text|private+void+button1_Click(object+sender,+EventArgs+e)
{
++++string+code+=+textBox1.Text;
++++string+sBarcode+=+string.Empty;
++++sBarcode+=+IsValidGtin(code);
++++lblBarCode.Text+=+sBarcode;
}
public+static+string+IsValidGtin(string+code)
{

++++//if+(code+!=+(new+Regex("[%5E0-9]")).Replace(code,+""))
++++//{
++++//++++//+is+not+numeric
++++//++++return+false;
++++//}
++++//+pad+with+zeros+to+lengthen+to+14+digits
++++switch+(code.Length)
++++{
++++++++case+2:
++++++++++++code+=+code+%2B+"000000000";
++++++++++++break;
++++++++case+3:
++++++++++++code+=+code+%2B+"00000000";
++++++++++++break;
++++++++case+4:
++++++++++++code+=+code+%2B+"0000000";
++++++++++++break;
++++++++case+5:
++++++++++++code+=+code+%2B+"000000";
++++++++++++break;
++++++++case+6:
++++++++++++code+=+code+%2B+"00000";
++++++++++++break;
++++++++case+7:
++++++++++++code+=+code+%2B+"0000";
++++++++++++break;
++++++++case+8:
++++++++++++code+=+code+%2B+"000";
++++++++++++break;
++++++++case+9:
++++++++++++code+=+code+%2B+"00";
++++++++++++break;
++++++++case+10:
++++++++++++code+=+code+%2B+"0";
++++++++++++break;
++++++++case+11:
++++++++++++break;
++++++++case+12:
++++++++++++code+=+code.Substring(0,+11);
++++++++++++break;
++++++++//default:
++++++++//+wrong+number+of+digits
++++++++//++return+false;
++++}
++++//+calculate+check+digit
++++int[]+a+=+new+int[12];
++++a[0]+=+int.Parse(code[0].ToString())+*+3;
++++a[1]+=+int.Parse(code[1].ToString());
++++a[2]+=+int.Parse(code[2].ToString())+*+3;
++++a[3]+=+int.Parse(code[3].ToString());
++++a[4]+=+int.Parse(code[4].ToString())+*+3;
++++a[5]+=+int.Parse(code[5].ToString());
++++a[6]+=+int.Parse(code[6].ToString())+*+3;
++++a[7]+=+int.Parse(code[7].ToString());
++++a[8]+=+int.Parse(code[8].ToString())+*+3;
++++a[9]+=+int.Parse(code[9].ToString());
++++a[10]+=+int.Parse(code[10].ToString())+*+3;
++++//a[11]+=+int.Parse(code[11].ToString());
++++//a[12]+=+int.Parse(code[12].ToString())+*+3;
++++int+sum+=+a[0]+%2B+a[1]+%2B+a[2]+%2B+a[3]+%2B+a[4]+%2B+a[5]+%2B+a[6]+%2B+a[7]+%2B+a[8]+%2B+a[9]+%2B+a[10];
++++string+check+=+Convert.ToString((10+-+(sum+%25+10)));
++++//+evaluate+check+digit
++++//+int+last+=+int.Parse(code[13].ToString());
++++//+return+check+==+last;
++++code+=+code+%2B+check;
++++return+code;
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|595979|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>private void button1_Click(object sender, EventArgs e)
{
 string code = textBox1.Text;
 string sBarcode = string.Empty;
 sBarcode = IsValidGtin(code);
 lblBarCode.Text = sBarcode;
}
public static string IsValidGtin(string code)
{

 //if (code != (new Regex("[^0-9]")).Replace(code, ""))
 //{
 // // is not numeric
 // return false;
 //}
 // pad with zeros to lengthen to 14 digits
 switch (code.Length)
 {
 case 2:
 code = code + "000000000";
 break;
 case 3:
 code = code + "00000000";
 break;
 case 4:
 code = code + "0000000";
 break;
 case 5:
 code = code + "000000";
 break;
 case 6:
 code = code + "00000";
 break;
 case 7:
 code = code + "0000";
 break;
 case 8:
 code = code + "000";
 break;
 case 9:
 code = code + "00";
 break;
 case 10:
 code = code + "0";
 break;
 case 11:
 break;
 case 12:
 code = code.Substring(0, 11);
 break;
 //default:
 // wrong number of digits
 // return false;
 }
 // calculate check digit
 int[] a = new int[12];
 a[0] = int.Parse(code[0].ToString()) * 3;
 a[1] = int.Parse(code[1].ToString());
 a[2] = int.Parse(code[2].ToString()) * 3;
 a[3] = int.Parse(code[3].ToString());
 a[4] = int.Parse(code[4].ToString()) * 3;
 a[5] = int.Parse(code[5].ToString());
 a[6] = int.Parse(code[6].ToString()) * 3;
 a[7] = int.Parse(code[7].ToString());
 a[8] = int.Parse(code[8].ToString()) * 3;
 a[9] = int.Parse(code[9].ToString());
 a[10] = int.Parse(code[10].ToString()) * 3;
 //a[11] = int.Parse(code[11].ToString());
 //a[12] = int.Parse(code[12].ToString()) * 3;
 int sum = a[0] + a[1] + a[2] + a[3] + a[4] + a[5] + a[6] + a[7] + a[8] + a[9] + a[10];
 string check = Convert.ToString((10 - (sum % 10)));
 // evaluate check digit
 // int last = int.Parse(code[13].ToString());
 // return check == last;
 code = code + check;
 return code;
}
</code></pre>

blocks|key|380052|text|GS1+US在PDF文档中发布了GTIN的校验位计算算法(删除了不断变化的链接)。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|380053|以下代码使用linq检查GTIN条形码的最后一位:+GTIN-8、GTIN-12+(UPC)、GTIN-13+(EAN)和GTIN-14+(ITF-14)。|380054|private+static+Regex+_gtinRegex+=+new+System.Text.RegularExpressions.Regex("%5E(\\d{8}%7C\\d{12,14})$");
public+static+bool+IsValidGtin(string+code)
{
++++if+(!(_gtinRegex.IsMatch(code)))+return+false;+//+check+if+all+digits+and+with+8,+12,+13+or+14+digits
++++code+=+code.PadLeft(14,+'0');+//+stuff+zeros+at+start+to+garantee+14+digits
++++int[]+mult+=+Enumerable.Range(0,+13).Select(i+=>+((int)(code[i]+-+'0'))+*+((i+%25+2+==+0)+?+3+:+1)).ToArray();+//+STEP+1:+without+check+digit,+"Multiply+value+of+each+position"+by+3+or+1
++++int+sum+=+mult.Sum();+//+STEP+2:+"Add+results+together+to+create+sum"
++++return+(10+-+(sum+%25+10))+%25+10+==+int.Parse(code[13].ToString());+//+STEP+3+Equivalent+to+"Subtract+the+sum+from+the+nearest+equal+or+higher+multiple+of+ten+=+CHECK+DIGIT"
}|code-block|syntax|javascript|380055|entityMap|0|LINK|mutability|MUTABLE|url|http://www.gs1us.org/^0|0|6|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

<a href="http://www.gs1us.org/">GS1 US</a> publishes the check digit calculation algorithm for GTIN in 
a PDF document (removed the constantly changing link).

The following code uses linq to check the last digit for GTIN barcodes: GTIN-8, GTIN-12 (UPC), GTIN-13 (EAN) and GTIN-14 (ITF-14).

<pre><code>private static Regex _gtinRegex = new System.Text.RegularExpressions.Regex("^(\\d{8}|\\d{12,14})$");
public static bool IsValidGtin(string code)
{
 if (!(_gtinRegex.IsMatch(code))) return false; // check if all digits and with 8, 12, 13 or 14 digits
 code = code.PadLeft(14, '0'); // stuff zeros at start to garantee 14 digits
 int[] mult = Enumerable.Range(0, 13).Select(i =&gt; ((int)(code[i] - '0')) * ((i % 2 == 0) ? 3 : 1)).ToArray(); // STEP 1: without check digit, "Multiply value of each position" by 3 or 1
 int sum = mult.Sum(); // STEP 2: "Add results together to create sum"
 return (10 - (sum % 10)) % 10 == int.Parse(code[13].ToString()); // STEP 3 Equivalent to "Subtract the sum from the nearest equal or higher multiple of ten = CHECK DIGIT"
}
</code></pre>

blocks|key|596066|text|///+<summary>
///+Validates+a+GTIN+(UPC/EAN)+using+the+terminating+check+digit
///+</summary>
///+<param+name="code">the+string+representing+the+GTIN</param>
///+<returns>True+if+the+check+digit+matches,+false+if+the+code+is+not+
///+parsable+as+a+GTIN+or+the+check+digit+does+not+match</returns>
public+static+bool+IsValidGtin(string+code)
{
++++if+(string.IsNullOrWhiteSpace(code))
++++++++return+false;
++++if+(code.Length+!=+8+&&+code.Length+!=+12+&&+code.Length+!=+13+
++++++++&&+code.Length+!=+14)
++++++++//+wrong+number+of+digits
++++++++return+false;

++++int+sum+=+0;
++++for+(int+i+=+0;+i+<+code.Length+-+1+/*+do+not+include+check+char+*/;+i%2B%2B)
++++{
++++++++if+(!char.IsNumber(code[i]))
++++++++++++return+false;

++++++++var+cchari+=+(int)char.GetNumericValue(code[i]);
++++++++//+even+(from+the+right)+characters+get+multiplied+by+3
++++++++//+add+the+length+to+align+right
++++++++if+((code.Length+%2B+i)+%25+2+==+0)
++++++++++++sum+%2B=+cchari+*+3;
++++++++else
++++++++++++sum+%2B=+cchari;
++++}

++++//+validate+check+char
++++char+checkChar+=+code[code.Length+-+1];
++++if+(!char.IsNumber(checkChar))
++++++++return+false;

++++int+checkChari+=+(int)char.GetNumericValue(checkChar);
++++return+checkChari+==+(10+-+(sum+%25+10))+%25+10;
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|596067|测试用例：|unstyled|596068|++++[TestMethod()]
++++public+void+IsValidGtinTest_Valid()
++++{
++++++++string[]+valid+=+new[]+{
++++++++++++"085126880552",
++++++++++++"0085126880552",
++++++++++++"00085126880552",
++++++++++++"0786936226355",
++++++++++++"0719852136552"
++++++++};
++++++++foreach+(var+upc+in+valid)
++++++++++++Assert.IsTrue(IdentifierUtilities.IsValidGtin(upc),+upc);
++++}

++++[TestMethod()]
++++public+void+IsValidGtinTest_Invalid()
++++{
++++++++string[]+invalid+=+new[]+{
++++++++++++"0058126880552",
++++++++++++"58126880552",
++++++++++++"0786936223655",
++++++++++++"0719853136552",
++++++++++++"",
++++++++++++"00",
++++++++++++null,
++++++++++++"123456789123456789123456789",
++++++++++++"1111111111111"
++++++++};
++++++++foreach+(var+upc+in+invalid)
++++++++++++Assert.IsFalse(IdentifierUtilities.IsValidGtin(upc),+upc);
++++}|596069|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|L|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|I|3|-4|5|F|7|N|8|@]|9|@]|A|$]]]|J|$]]

<pre><code>/// &lt;summary&gt;
/// Validates a GTIN (UPC/EAN) using the terminating check digit
/// &lt;/summary&gt;
/// &lt;param name="code"&gt;the string representing the GTIN&lt;/param&gt;
/// &lt;returns&gt;True if the check digit matches, false if the code is not 
/// parsable as a GTIN or the check digit does not match&lt;/returns&gt;
public static bool IsValidGtin(string code)
{
 if (string.IsNullOrWhiteSpace(code))
 return false;
 if (code.Length != 8 &amp;&amp; code.Length != 12 &amp;&amp; code.Length != 13 
 &amp;&amp; code.Length != 14)
 // wrong number of digits
 return false;

 int sum = 0;
 for (int i = 0; i &lt; code.Length - 1 /* do not include check char */; i++)
 {
 if (!char.IsNumber(code[i]))
 return false;

 var cchari = (int)char.GetNumericValue(code[i]);
 // even (from the right) characters get multiplied by 3
 // add the length to align right
 if ((code.Length + i) % 2 == 0)
 sum += cchari * 3;
 else
 sum += cchari;
 }

 // validate check char
 char checkChar = code[code.Length - 1];
 if (!char.IsNumber(checkChar))
 return false;

 int checkChari = (int)char.GetNumericValue(checkChar);
 return checkChari == (10 - (sum % 10)) % 10;
}
</code></pre>

Test cases:

<pre><code> [TestMethod()]
 public void IsValidGtinTest_Valid()
 {
 string[] valid = new[] {
 "085126880552",
 "0085126880552",
 "00085126880552",
 "0786936226355",
 "0719852136552"
 };
 foreach (var upc in valid)
 Assert.IsTrue(IdentifierUtilities.IsValidGtin(upc), upc);
 }

 [TestMethod()]
 public void IsValidGtinTest_Invalid()
 {
 string[] invalid = new[] {
 "0058126880552",
 "58126880552",
 "0786936223655",
 "0719853136552",
 "",
 "00",
 null,
 "123456789123456789123456789",
 "1111111111111"
 };
 foreach (var upc in invalid)
 Assert.IsFalse(IdentifierUtilities.IsValidGtin(upc), upc);
 }
</code></pre>

blocks|key|596099|text|++++private+bool+ValidateCheckDigit()
++++{

++++++++Int32+_num+=+0;
++++++++Int32+_checkdigit+=+0;

++++++++for+(int+i+=+0;+i+<+CurrentUpcInfo.UpcCode.Length;+i%2B%2B)
++++++++{
++++++++++++if+(i+%25+2+==+0)
++++++++++++{
++++++++++++++++_num+%2B=+(3+*+Convert.ToInt32(CurrentUpcInfo.UpcCode.Substring(i,+1)));
++++++++++++}
++++++++++++else
++++++++++++{
++++++++++++++++_num+%2B=+Convert.ToInt32(CurrentUpcInfo.UpcCode.Substring(i,+1));
++++++++++++}

++++++++}
++++++++_num+=+Math.Abs(_num)+%2B+10;++//+in+case+num+is+a+zero
++++++++_checkdigit+=+(10+-+(_num+%25+10))+%25+10;


++++++++if+(Convert.ToInt32(CurrentUpcInfo.Checkdigit)+==+_checkdigit)
++++++++++++return+true;

++++++++return+false;

++++}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|596100|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code> private bool ValidateCheckDigit()
 {

 Int32 _num = 0;
 Int32 _checkdigit = 0;

 for (int i = 0; i &lt; CurrentUpcInfo.UpcCode.Length; i++)
 {
 if (i % 2 == 0)
 {
 _num += (3 * Convert.ToInt32(CurrentUpcInfo.UpcCode.Substring(i, 1)));
 }
 else
 {
 _num += Convert.ToInt32(CurrentUpcInfo.UpcCode.Substring(i, 1));
 }

 }
 _num = Math.Abs(_num) + 10; // in case num is a zero
 _checkdigit = (10 - (_num % 10)) % 10;


 if (Convert.ToInt32(CurrentUpcInfo.Checkdigit) == _checkdigit)
 return true;

 return false;

 }
</code></pre>

blocks|key|380160|text|我也遇到了类似的问题，google把我带到了这个页面。我需要为标签生成程序计算大量条形码的校验位。我首先从上面Luciano+Carvalho的答案的一个变体开始，但我对字符串到字符的转换到整数的转换有一点好奇。我怀疑我也许能够提高一点性能。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|380161|请注意，验证是在此函数之外进行的。由于我正在生成大量条形码，因此此函数更多地是为了提高速度而构建的。|380162|int+CalculateCheckDigit(ulong+label)
{
++++int+sum+=+0;
++++bool+isEven=true;
++++while(label>0)
++++{
++++++++if(isEven)
++++++++++++sum+%2B=+(int)(label+%25+10)+*+3;
++++++++else
++++++++++++sum+%2B=+(int)(label+%25+10)+*+1;
++++++++isEven+=+!isEven;
++++++++label+/=+10;
++++}

++++return+(10+-+(sum+%25+10))+%25+10;
}|code-block|syntax|javascript|380163|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I had a similar problem and google brought me to this page. 
I needed to calculate the check digit for a large number of barcodes for a label generating program. I first started with a variation of Luciano Carvalho's answer above, but I was a little curious of the casting of the string to a char to an int. I suspected I might be able improve the performance a bit.

Please note that validating is happening outside of this function. This function is built more for speed since I am generating a large number of barcodes.

<pre><code>int CalculateCheckDigit(ulong label)
{
 int sum = 0;
 bool isEven=true;
 while(label&gt;0)
 {
 if(isEven)
 sum += (int)(label % 10) * 3;
 else
 sum += (int)(label % 10) * 1;
 isEven = !isEven;
 label /= 10;
 }

 return (10 - (sum % 10)) % 10;
}
</code></pre>

blocks|key|596219|text|我知道这个问题是在.net/C#的上下文中出现的。尽管如此，我还是在Groovy上下文中找到了相同问题的答案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|596220|由于我实际上成功地使用了这个页面上的信息来提出我自己的问题的答案，我想我应该分享一下结果。|596221|特别是AlexDev，Zack+Peterson和Mitch的回答对我很有帮助。|596222|/*
Check+digit+calculation+is+based+on+modulus+10+with+digits+in+an+odd
position+(from+right+to+left)+being+weighted+1+and+even+position+digits
being+weighted+3.+
For+further+information+on+EAN-13+see:
Wikipedia+-+European+Article+Number:+http://en.wikipedia.org/wiki/International_Article_Number_%2528EAN%2529
Implementation+based+on+http://stackoverflow.com/questions/10143547/how-do-i-validate-a-upc-or-ean-code
Tests+can+be+found+there+too
*/
boolean+isValidEan(String+code){
++returnValue+=+false
++if+(code+==~+/\d{8}%7C\d{12,14}/){+//Matches+if+String+code+contains+8,+12,+13+or+14+digits
++++assert+[8,12,13,14].contains(code.size())
++++code+=+code.padLeft(14,+'0')
++++assert+code.size()+==+14
++++int+sum+=+0
++++code.eachWithIndex{+c,+i+->
++++++sum+%2B=+c.toInteger()+*+((i+%25+2+==+0)+?+3+:+1)
++++}
++++returnValue+=+sum+%25+10+==+0
++}
++return+returnValue
}|code-block|syntax|javascript|596223|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|O|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|P|8|@]|9|@]|A|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I'm aware that the question is in the context of .net/C#. Nevertheless I landed on this page seeking answer to the same question, but in a Groovy context. 
 
Since I actually succeeded in using the information on this page to come up with an answer to my own problem, I thought I'd share the result. 
Especially the answers from AlexDev, Zack Peterson and Mitch was helpful to me.

<pre><code>/*
Check digit calculation is based on modulus 10 with digits in an odd
position (from right to left) being weighted 1 and even position digits
being weighted 3. 
For further information on EAN-13 see:
Wikipedia - European Article Number: http://en.wikipedia.org/wiki/International_Article_Number_%28EAN%29
Implementation based on http://stackoverflow.com/questions/10143547/how-do-i-validate-a-upc-or-ean-code
Tests can be found there too
*/
boolean isValidEan(String code){
 returnValue = false
 if (code ==~ /\d{8}|\d{12,14}/){ //Matches if String code contains 8, 12, 13 or 14 digits
 assert [8,12,13,14].contains(code.size())
 code = code.padLeft(14, '0')
 assert code.size() == 14
 int sum = 0
 code.eachWithIndex{ c, i -&gt;
 sum += c.toInteger() * ((i % 2 == 0) ? 3 : 1)
 }
 returnValue = sum % 10 == 0
 }
 return returnValue
}
</code></pre>

blocks|key|596251|text|def+check_digit()：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|596252|++++++++users_gtin=raw_input("enter+first+seven+digits+of+gtin+")

++++++++gtin_seven_digits=unicode(users_gtin)
++++++++
++++++++
++++++++if+len(gtin_seven_digits)+==+7+and+gtin_seven_digits.isnumeric():
++++++++++++ck+=+((((int(gtin_seven_digits[0]))+%2B+(int(gtin_seven_digits[2]))+%2B+(int(gtin_seven_digits[4]))+%2B+(int(gtin_seven_digits[6])))*3)+%2B+((int(gtin_seven_digits[1]))+%2B+(int(gtin_seven_digits[3]))+%2B+(int(gtin_seven_digits[5]))))+%2510
++++++++++++final_ck+=+10-ck

++++++++++++if+final_ck+==+10:
++++++++++++++++final_ck=0
++++++++++++++++print+"Is+your+check+digit",final_ck,"?"
++++++++
++++++++++++else:
++++++++++++++++print+"Is+your+check+digit",final_ck,"?"
++++++++++++++++
++++++++else:
++++++++++++print+"please+try+typing+an+seven+digit+number"
++++++++++++check_digit()
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++choice=raw_input("enter+(a)+to+restart+or+press+anything+other+than+the+letter++a++to+end+this+program+<<<<+").upper()
++++++++

++++++++if+choice+==+"A":
++++++++++++check_digit()|code-block|syntax|javascript|596253|check_digit()|596254|可能不是最有效的，但希望它能有所帮助..|596255|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

def check_digit():
<pre><code> users_gtin=raw_input(&quot;enter first seven digits of gtin &quot;)

 gtin_seven_digits=unicode(users_gtin)
 
 
 if len(gtin_seven_digits) == 7 and gtin_seven_digits.isnumeric():
 ck = ((((int(gtin_seven_digits[0])) + (int(gtin_seven_digits[2])) + (int(gtin_seven_digits[4])) + (int(gtin_seven_digits[6])))*3) + ((int(gtin_seven_digits[1])) + (int(gtin_seven_digits[3])) + (int(gtin_seven_digits[5])))) %10
 final_ck = 10-ck

 if final_ck == 10:
 final_ck=0
 print &quot;Is your check digit&quot;,final_ck,&quot;?&quot;
 
 else:
 print &quot;Is your check digit&quot;,final_ck,&quot;?&quot;
 
 else:
 print &quot;please try typing an seven digit number&quot;
 check_digit()
 

 choice=raw_input(&quot;enter (a) to restart or press anything other than the letter a to end this program &lt;&lt;&lt;&lt; &quot;).upper()
 

 if choice == &quot;A&quot;:
 check_digit()
 
</code></pre>
check_digit()
<h1>probably not the most efficient but hope it helps..</h1>

blocks|key|380298|text|我找到了这个Nuget包：https://www.nuget.org/packages/ProductCodeValidator/|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|380299|github中的代码是：https://github.com/ThomasPe/ProductCodeValidator。|380300|下面是它的使用方法：|380301|using+ProductCodeValidator;

bool+IsValidEAN(string+EAN)
{
++++return+EanValidator.IsValidEan(testEan));
}|code-block|syntax|javascript|380302|entityMap|0|LINK|mutability|MUTABLE|url|https://www.nuget.org/packages/ProductCodeValidator/|1|https://github.com/ThomasPe/ProductCodeValidator^0|D|1G|0|0|C|1C|1|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]]|C|$]]|$1|F|3|G|5|6|7|14|8|@]|9|@]|C|$]]|$1|H|3|I|5|J|7|15|8|@]|9|@]|C|$K|L]]|$1|M|3|-4|5|6|7|16|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]|U|$5|P|Q|R|C|$S|V]]]]

I Found this Nuget Package: <a href="https://www.nuget.org/packages/ProductCodeValidator/" rel="nofollow noreferrer">https://www.nuget.org/packages/ProductCodeValidator/</a>

The code in github is: <a href="https://github.com/ThomasPe/ProductCodeValidator" rel="nofollow noreferrer">https://github.com/ThomasPe/ProductCodeValidator</a>.

Here's how to use it:

<pre><code>using ProductCodeValidator;

bool IsValidEAN(string EAN)
{
 return EanValidator.IsValidEan(testEan));
}
</code></pre>

blocks|key|596355|text|根据卢西亚诺的回答。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|596356|我删除了Linq依赖，因为我在Java中也需要它。删除了14位的填充，以便它可以用于计算更长的ITF条形码的校验位。|596357|长度不均匀的代码由用于长度不均匀的代码的31313模式13131的(i+%2B+code.Length+%25+2)来处理。它避免创建对象，并花费134毫秒(在我的PC上)来计算所有EAN-8代码的校验数字。|offset|length|style|CODE|596358|我知道问题是关于IsValidEan()方法的，但是如果你有一个带有方法的库，你可能无论如何都需要这个库。在长度和其他校验之后，IsValidEan()应调用此函数进行校验位验证。|596359|///+<summary>
///+Calculate+check+digit+for+UPC-A,+EAN-13,+ITF-14+(or+any+ITF)
///+</summary>
///+<param+name="code">This+should+include+the+check+digit+(append+a+fake+check+digit+if+needed)</param>
///+<returns></returns>
public+static+char+CalculateCheckDigit(string+code)
{
 + +//+Don't+include+check+digit+in+the+sum+(<+code.Length+-+1)
 + +int+sum+=+0;
 + +for+(int+i+=+0;+i+<+code.Length+-+1;+i%2B%2B)
 + + + +sum+%2B=+(code[i]+-+'0')+*+(((i+%2B+code.Length+%25+2)+%25+2+==+0)+?+3+:+1);

 + +return+(char)((10+-+(sum+%25+10))+%25+10+%2B+'0');
}|code-block|syntax|javascript|596360|Java版本：|596361|public+static+char+CalculateCheckDigit(String+code)+{
 + +int+sum+=+0;
 + +for(int+i+=+0;+i+<+code.length()+-+1;+i%2B%2B)
 + + + +sum+%2B=+((int)code.charAt(i)+-+(int)'0')+*+(((i+%2B+code.length()+%25+2)+%25+2+==+0)+?+3+:+1);

 + +return+(char)((10+-+(sum+%25+10))+%25+10+%2B+(int)'0');
}|596362|entityMap^0|0|0|K|5|R|5|X|L|0|8|C|1S|C|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Y|8|@$F|Z|G|10|H|I]|$F|11|G|12|H|I]|$F|13|G|14|H|I]]|9|@]|A|$]]|$1|J|3|K|5|6|7|15|8|@$F|16|G|17|H|I]|$F|18|G|19|H|I]]|9|@]|A|$]]|$1|L|3|M|5|N|7|1A|8|@]|9|@]|A|$O|P]]|$1|Q|3|R|5|6|7|1B|8|@]|9|@]|A|$]]|$1|S|3|T|5|N|7|1C|8|@]|9|@]|A|$O|P]]|$1|U|3|-4|5|6|7|1D|8|@]|9|@]|A|$]]]|V|$]]

Based on Luciano's answer.

I removed the Linq dependency because I needed it in Java too. Removed padding to 14 digits so it may be used for calculating check digits of longer ITF barcodes.

Codes of uneven length are handled by the <code>(i + code.Length % 2)</code> that makes the <code>31313</code> pattern <code>13131</code> for codes of uneven length. It avoids creating objects and takes 134 ms (on my PC) to calculate the check digits for all EAN-8 codes.

I know the question was about a <code>IsValidEan()</code> method, but if you a have library with methods you would probably need this one anyway. <code>IsValidEan()</code> should call this for check digit verification after length and other checks.

<pre><code>/// &lt;summary&gt;
/// Calculate check digit for UPC-A, EAN-13, ITF-14 (or any ITF)
/// &lt;/summary&gt;
/// &lt;param name="code"&gt;This should include the check digit (append a fake check digit if needed)&lt;/param&gt;
/// &lt;returns&gt;&lt;/returns&gt;
public static char CalculateCheckDigit(string code)
{
    // Don't include check digit in the sum (&lt; code.Length - 1)
    int sum = 0;
    for (int i = 0; i &lt; code.Length - 1; i++)
        sum += (code[i] - '0') * (((i + code.Length % 2) % 2 == 0) ? 3 : 1);

    return (char)((10 - (sum % 10)) % 10 + '0');
}
</code></pre>

Java version:

<pre><code>public static char CalculateCheckDigit(String code) {
    int sum = 0;
    for(int i = 0; i &lt; code.length() - 1; i++)
        sum += ((int)code.charAt(i) - (int)'0') * (((i + code.length() % 2) % 2 == 0) ? 3 : 1);

    return (char)((10 - (sum % 10)) % 10 + (int)'0');
}
</code></pre>

blocks|key|596383|text|我编写这段Python代码是为了快速简洁地验证UPC代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|596384|def+upc_validate(upc):
++++#+check+if+upc+is+exactly+12+digits
++++upc+=+str(upc)
++++if+len(upc)+!=+12+or+len(list(filter(lambda+x:+48+<=+ord(x)+<=+57,+upc)))+!=+12:
++++++++return+False

++++#+validate+CRC+/+check+digit+(sum+of+digits+is+a+product+of+10+after+multiplying+each+odd+digit+by+CRC)
++++digits+=+list(map(int,+upc))
++++crc+=+digits[-1]
++++total+=+sum([digit+if+i+&+1+else+digit+*+crc+for+i,+digit+in+enumerate(digits)])
++++return+total+%25+10+==+0|code-block|syntax|javascript|596385|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I wrote this Python code to validate UPC codes quickly and succinctly:

<pre><code>def upc_validate(upc):
 # check if upc is exactly 12 digits
 upc = str(upc)
 if len(upc) != 12 or len(list(filter(lambda x: 48 &lt;= ord(x) &lt;= 57, upc))) != 12:
 return False

 # validate CRC / check digit (sum of digits is a product of 10 after multiplying each odd digit by CRC)
 digits = list(map(int, upc))
 crc = digits[-1]
 total = sum([digit if i &amp; 1 else digit * crc for i, digit in enumerate(digits)])
 return total % 10 == 0
</code></pre>

blocks|key|380432|text|在克利伯/港湾，适用于EAN8、EAN12、EAN13、EAN14|type|unstyled|depth|inlineStyleRanges|entityRanges|data|380433|function+DigitEan(cCodigo)
++++local+cCode+:=+AllTrim(cCodigo)
++++local+nLen+:=+Len(cCode)
++++local+cc+:=+0
++++local+i+:=+0

++++for+i:=1+to+nLen-1
++++++++cc%2B=(asc(substr(cCode,nLen-i,1))-48)*iif(i%252==0,1,3)
++++next

return+(+(10-(cc%2510))%2510+)|code-block|syntax|javascript|380434|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

In Clipper/Harbour for EAN8,EAN12,EAN13,EAN14
<pre><code>function DigitEan(cCodigo)
 local cCode := AllTrim(cCodigo)
 local nLen := Len(cCode)
 local cc := 0
 local i := 0

 for i:=1 to nLen-1
 cc+=(asc(substr(cCode,nLen-i,1))-48)*iif(i%2==0,1,3)
 next

return ( (10-(cc%10))%10 )
</code></pre>

blocks|key|596477|text|我还需要验证大量的EAN-13，当我搜索它时发现了这个问题。我不喜欢最受欢迎的答案的样子。在处理大型数据集时，可能的字符串分配过多。与仅验证每个字符是否为数字相比，正则表达式也变得很慢。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|596478|在我的旧笔记本电脑上，在8851EAN-13编号的数据集上运行最受欢迎的问题中使用的验证逻辑花费了47ms，而我自己的实现只用了2ms。这里的字符串分配也要少得多。|596479|private+static+bool+IsValidGtin(ReadOnlySpan<char>+input,+byte+length)
{
++++if+(input.Length+!=+length)
++++{
++++++++return+false;
++++}

++++if+(!char.IsDigit(input[%5E1]))
++++{
++++++++return+false;
++++}

++++var+sum+=+0d;
++++var+multiplyByThree+=+true;
++++var+inputWithoutCheckDigit+=+input[..%5E1];
++++for+(var+i+=+inputWithoutCheckDigit.Length+-+1;+i+>=+0;+i--)
++++{
++++++++var+currentChar+=+inputWithoutCheckDigit[i];
++++++++if+(!char.IsDigit(currentChar))
++++++++{
++++++++++++return+false;
++++++++}

++++++++var+value+=+char.GetNumericValue(currentChar);
++++++++if+(multiplyByThree)
++++++++{
++++++++++++sum+%2B=+value+*+3;
++++++++}
++++++++else
++++++++{
++++++++++++sum+%2B=+value;
++++++++}

++++++++multiplyByThree+=+!multiplyByThree;
++++}
++++
++++var+checkDigit+=+char.GetNumericValue(input[%5E1]);

++++return+(sum+%2B+checkDigit)+%25+10+==+0;

}|code-block|syntax|javascript|596480|如果需要，我写了更多关于它的细节here|offset|length|596481|entityMap|0|LINK|mutability|MUTABLE|url|https://nnss.eu/2021/03/algorithm-for-effecient-validation-of-ean-13-and-other-gtin-numbers/^0|0|0|0|G|4|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@$K|Y|L|Z|1|10]]|A|$]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

I also needed to validate a large number of EAN-13 and found this question when i searched for it. I didn't like the look of the most upvoted answer. Too many possible string allocations when working with a large dataset. The regex also turned out to be slow, compared to just validating if each char is a digit or not.
Running the validation logic used in the most upvoted question on my dataset of 8851 EAN-13 numbers took 47 ms on my old laptop, while my own implementation only took 2 ms.
There are also far fewer string allocations here.
<pre><code>private static bool IsValidGtin(ReadOnlySpan&lt;char&gt; input, byte length)
{
 if (input.Length != length)
 {
 return false;
 }

 if (!char.IsDigit(input[^1]))
 {
 return false;
 }

 var sum = 0d;
 var multiplyByThree = true;
 var inputWithoutCheckDigit = input[..^1];
 for (var i = inputWithoutCheckDigit.Length - 1; i &gt;= 0; i--)
 {
 var currentChar = inputWithoutCheckDigit[i];
 if (!char.IsDigit(currentChar))
 {
 return false;
 }

 var value = char.GetNumericValue(currentChar);
 if (multiplyByThree)
 {
 sum += value * 3;
 }
 else
 {
 sum += value;
 }

 multiplyByThree = !multiplyByThree;
 }
 
 var checkDigit = char.GetNumericValue(input[^1]);

 return (sum + checkDigit) % 10 == 0;

}
</code></pre>
I wrote more details about it <a href="https://nnss.eu/2021/03/algorithm-for-effecient-validation-of-ean-13-and-other-gtin-numbers/" rel="nofollow noreferrer">here</a> if needed

blocks|key|380543|text|我今天花了一些时间来完全支持GTIN-8、GTIN-12、GTIN-13和GTIN-14的校验和计算。大多数算法示例只支持GTIN-13或很难看。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|380544|那这个呢？|380545|public+static+char+CalculateCheckSumDigit(string+code)
{
+++//+https://www.gs1.org/services/how-calculate-check-digit-manually
+++var+reversed+=+code.Reverse().Skip(1);

+++int+sum+=+0;
+++int+multiplier+=+3;
+++foreach(char+c+in+reversed)
+++{
+++++++if+(multiplier+==+3)
+++++++{
+++++++++++sum+%2B=+(c+-+0x30)+*+multiplier;
+++++++++++multiplier+=+1;
+++++++}
+++++++else
+++++++{
+++++++++++sum+%2B=+(c+-+0x30)+*+multiplier;
+++++++++++multiplier+=+3;
+++++++}
+++}

+++int+closestTenth+=+(sum+%2B+9)+/+10+*+10;

+++return+(char)((closestTenth+-+sum)+%2B+0x30);
}|code-block|syntax|javascript|380546|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I spent some time today to fully support checksum calculation for GTIN-8, GTIN-12, GTIN-13 and GTIN-14. Most algorithm examples only supports GTIN-13 or are ugly.
What about this?
<pre><code>public static char CalculateCheckSumDigit(string code)
{
 // https://www.gs1.org/services/how-calculate-check-digit-manually
 var reversed = code.Reverse().Skip(1);

 int sum = 0;
 int multiplier = 3;
 foreach(char c in reversed)
 {
 if (multiplier == 3)
 {
 sum += (c - 0x30) * multiplier;
 multiplier = 1;
 }
 else
 {
 sum += (c - 0x30) * multiplier;
 multiplier = 3;
 }
 }

 int closestTenth = (sum + 9) / 10 * 10;

 return (char)((closestTenth - sum) + 0x30);
}
</code></pre>

blocks|key|596582|text|如果有人需要AlexDev答案的javascript版本，这里有。我注意到AlexDev的答案也适用于ITF条形码，而其他一些答案不适用。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|596583|function+isValidGtin(barcode)+{
++++var+code+=+"00000"+%2B+barcode;
++++code+=+code.substring(code.length+-+14);
++++var+sum+=+0;
++++for+(var+i+=+0;+i+<+code.length;+i%2B%2B)+{
++++++++sum+%2B=+code[i]+*+((i+%25+2+==+0)+?+3+:+1);
++++}
++++return+(sum+%25+10)+==+0;
}|code-block|syntax|javascript|596584|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

In case anyone needs a javascript version of AlexDev's answer, here goes. I noticed AlexDev's answer also works with ITF barcodes, where some other answers do not.
<pre><code>function isValidGtin(barcode) {
 var code = &quot;00000&quot; + barcode;
 code = code.substring(code.length - 14);
 var sum = 0;
 for (var i = 0; i &lt; code.length; i++) {
 sum += code[i] * ((i % 2 == 0) ? 3 : 1);
 }
 return (sum % 10) == 0;
}
</code></pre>

I need a C# .NET function to evaluate whether a typed or scanned barcode is a valid <a href="http://en.wikipedia.org/wiki/Global_Trade_Item_Number" rel="noreferrer">Global Trade Item Number</a> (UPC or EAN).

<img src="https://i.stack.imgur.com/CR80w.gif" alt="barcode check digit">

The last digit of a bar code number is a computer Check Digit which makes sure the bar code is correctly composed. <a href="http://www.gs1.org/barcodes/support/check_digit_calculator" rel="noreferrer">GTIN Check Digit Calculator</a>

How do I validate a UPC or EAN code?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我需要一个C# .NET函数来评估键入或扫描的条形码是否为有效的 (UPC或EAN)。​​条形码号码的最后一位是计算机校验位，它确保条形码的正确组成。

问如何验证UPC或EAN代码？
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问如何验证UPC或EAN代码？EN