blocks|key|730544|text|使用查询而不是函数：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|730545|DELETE+FROM+table1+AS+tb1+INNER+JOIN+
(SELECT+id,+COUNT(id)+AS+cntr+FROM+table1+GROUP+BY+id)+AS+tb2
ON+tb1.id+=+tb2.id+WHERE+tb2.cntr+>+1|code-block|syntax|javascript|730546|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|$]]

Use a query instead of functions:

<pre><code>DELETE FROM table1 AS tb1 INNER JOIN 
(SELECT id, COUNT(id) AS cntr FROM table1 GROUP BY id) AS tb2
ON tb1.id = tb2.id WHERE tb2.cntr &gt; 1
</code></pre>

blocks|key|1928912|text|如何删除重复行？。(调整查询以连接4个键列)|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1928913|编辑:使用您的新信息，我相信最简单的方法是实现IEqualityComparer并在数据行上使用Distinct。否则，如果您使用的是IEnumerable/IList而不是DataTable/DataRow，那么当然可以使用一些LINQ功夫。|1928914|编辑:示例IEqualityComparer|1928915|public+class+MyRowComparer+:+IEqualityComparer<DataRow>
{

++++public+bool+Equals(DataRow+x,+DataRow+y)
++++{
++++++++return+(x.Field<int>("ID")+==+y.Field<int>("ID"))+&&
++++++++++++string.Compare(x.Field<string>("Name"),+y.Field<string>("Name"),+true)+==+0+&&
++++++++++...+//+extend+this+to+include+all+your+4+keys...
++++}

++++public+int+GetHashCode(DataRow+obj)
++++{
++++++++return+obj.Field<int>("ID").GetHashCode()+%5E+obj.Field<string>("Name").GetHashCode()+etc.
++++}
}|code-block|syntax|javascript|1928916|你可以这样使用它：|1928917|var+uniqueRows+=+myTable.AsEnumerable().Distinct(MyRowComparer);|1928918|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/18932/sql-how-can-i-remove-duplicate-rows^0|0|8|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]]|C|$]]|$1|D|3|E|5|6|7|12|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|13|8|@]|9|@]|C|$]]|$1|H|3|I|5|J|7|14|8|@]|9|@]|C|$K|L]]|$1|M|3|N|5|6|7|15|8|@]|9|@]|C|$]]|$1|O|3|P|5|J|7|16|8|@]|9|@]|C|$K|L]]|$1|Q|3|-4|5|6|7|17|8|@]|9|@]|C|$]]]|R|$S|$5|T|U|V|C|$W|X]]]]

<a href="https://stackoverflow.com/questions/18932/sql-how-can-i-remove-duplicate-rows">How can I remove duplicate rows?</a>. (Adjust the query there to join on your 4 key columns)

EDIT: with your new information I believe the easiest way would be to implement IEqualityComparer&lt;T&gt; and use Distinct on your data rows. Otherwise if you're working with IEnumerable/IList instead of DataTable/DataRow, it is certainly possible with some LINQ-to-objects kung-fu.

EDIT: example IEqualityComparer

<pre><code>public class MyRowComparer : IEqualityComparer&lt;DataRow&gt;
{

 public bool Equals(DataRow x, DataRow y)
 {
 return (x.Field&lt;int&gt;("ID") == y.Field&lt;int&gt;("ID")) &amp;&amp;
 string.Compare(x.Field&lt;string&gt;("Name"), y.Field&lt;string&gt;("Name"), true) == 0 &amp;&amp;
 ... // extend this to include all your 4 keys...
 }

 public int GetHashCode(DataRow obj)
 {
 return obj.Field&lt;int&gt;("ID").GetHashCode() ^ obj.Field&lt;string&gt;("Name").GetHashCode() etc.
 }
}
</code></pre>

You can use it like this:

<pre><code>var uniqueRows = myTable.AsEnumerable().Distinct(MyRowComparer);
</code></pre>

blocks|key|1928937|text|如果您能够访问Linq，我认为您应该能够在内存集合上使用内置组功能，并选择重复的行。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1928938|搜索Google查找Linq的示例|1928939|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

If you have access to Linq I think you should be able to use the built in group functionality on the in memory collection and pick out the duplicate rows

Search Google for Linq Group by for examples

blocks|key|1928944|text|您可以将Linq用于数据集。检查这。就像这样：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1928945|//+Fill+the+DataSet.
DataSet+ds+=+new+DataSet();
ds.Locale+=+CultureInfo.InvariantCulture;
FillDataSet(ds);

List<DataRow>+rows+=+new+List<DataRow>();

DataTable+contact+=+ds.Tables["Contact"];

//+Get+100+rows+from+the+Contact+table.
IEnumerable<DataRow>+query+=+(from+c+in+contact.AsEnumerable()
++++++++++++++++++++++++++++++select+c).Take(100);

DataTable+contactsTableWith100Rows+=+query.CopyToDataTable();

//+Add+100+rows+to+the+list.
foreach+(DataRow+row+in+contactsTableWith100Rows.Rows)
++++rows.Add(row);

//+Create+duplicate+rows+by+adding+the+same+100+rows+to+the+list.
foreach+(DataRow+row+in+contactsTableWith100Rows.Rows)
++++rows.Add(row);

DataTable+table+=
++++System.Data.DataTableExtensions.CopyToDataTable<DataRow>(rows);

//+Find+the+unique+contacts+in+the+table.
IEnumerable<DataRow>+uniqueContacts+=
++++table.AsEnumerable().Distinct(DataRowComparer.Default);

Console.WriteLine("Unique+contacts:");
foreach+(DataRow+uniqueContact+in+uniqueContacts)
{
++++Console.WriteLine(uniqueContact.Field<Int32>("ContactID"));
}|code-block|syntax|javascript|1928946|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/bb669119.aspx^0|G|1|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

You can use Linq to Datasets. Check <a href="http://msdn.microsoft.com/en-us/library/bb669119.aspx" rel="noreferrer">this</a>. Something like this:

<pre><code>// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);

List&lt;DataRow&gt; rows = new List&lt;DataRow&gt;();

DataTable contact = ds.Tables["Contact"];

// Get 100 rows from the Contact table.
IEnumerable&lt;DataRow&gt; query = (from c in contact.AsEnumerable()
 select c).Take(100);

DataTable contactsTableWith100Rows = query.CopyToDataTable();

// Add 100 rows to the list.
foreach (DataRow row in contactsTableWith100Rows.Rows)
 rows.Add(row);

// Create duplicate rows by adding the same 100 rows to the list.
foreach (DataRow row in contactsTableWith100Rows.Rows)
 rows.Add(row);

DataTable table =
 System.Data.DataTableExtensions.CopyToDataTable&lt;DataRow&gt;(rows);

// Find the unique contacts in the table.
IEnumerable&lt;DataRow&gt; uniqueContacts =
 table.AsEnumerable().Distinct(DataRowComparer.Default);

Console.WriteLine("Unique contacts:");
foreach (DataRow uniqueContact in uniqueContacts)
{
 Console.WriteLine(uniqueContact.Field&lt;Int32&gt;("ContactID"));
}
</code></pre>

blocks|key|730882|text|利格特78的答案要好得多，尤其是。因为我的错了！更正如下..。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|730883|DELETE+TableWithDuplicates
++++FROM+TableWithDuplicates
++++++++LEFT+OUTER+JOIN+(
++++++++++++SELECT+PK_ID+=+Min(PK_ID),+--Decide+your+method+for+deciding+which+rows+to+keep
++++++++++++++++KeyColumn1,
++++++++++++++++KeyColumn2,
++++++++++++++++KeyColumn3,
++++++++++++++++KeyColumn4
++++++++++++++++FROM+TableWithDuplicates
++++++++++++++++GROUP+BY+KeyColumn1,
++++++++++++++++++++KeyColumn2,
++++++++++++++++++++KeyColumn3,
++++++++++++++++++++KeyColumn4
++++++++++++)+AS+RowsToKeep
++++++++++++ON+TableWithDuplicates.PK_ID+=+RowsToKeep.PK_ID
++++WHERE+RowsToKeep.PK_ID+IS+NULL|code-block|syntax|javascript|730884|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|$]]

Liggett78's answer is much better - esp. as mine had an error! Correction as follows...

<pre><code>DELETE TableWithDuplicates
 FROM TableWithDuplicates
 LEFT OUTER JOIN (
 SELECT PK_ID = Min(PK_ID), --Decide your method for deciding which rows to keep
 KeyColumn1,
 KeyColumn2,
 KeyColumn3,
 KeyColumn4
 FROM TableWithDuplicates
 GROUP BY KeyColumn1,
 KeyColumn2,
 KeyColumn3,
 KeyColumn4
 ) AS RowsToKeep
 ON TableWithDuplicates.PK_ID = RowsToKeep.PK_ID
 WHERE RowsToKeep.PK_ID IS NULL
</code></pre>

blocks|key|393849|text|在bytes.com上找到了这个|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|393850|您可以使用JET+4.0+OLE+DB提供程序和System.Data.OleDb命名空间中的类来访问逗号分隔的文本文件(使用DataSet/DataTable)。
或者，您可以在System.Data.Odbc命名空间中的类中使用Microsoft文本驱动程序来使用ODBC驱动程序访问文件。|blockquote|393851|这将允许您像其他人所建议的那样，通过sql查询访问数据。|393852|entityMap|0|LINK|mutability|MUTABLE|url|http://bytes.com/groups/net-c/278990-whats-best-way-read-csv-file-c#post1115863^0|1|9|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$]]|$1|G|3|H|5|6|7|V|8|@]|9|@]|C|$]]|$1|I|3|-4|5|6|7|W|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Found this on <a href="http://bytes.com/groups/net-c/278990-whats-best-way-read-csv-file-c#post1115863" rel="nofollow noreferrer">bytes.com</a>:

<blockquote>
 You can use the JET 4.0 OLE DB provider with the classes in the
 System.Data.OleDb namespace to access the comma delimited text file (using a
 DataSet/DataTable).
 
 Or you could use Microsoft Text Driver for ODBC with the classes in the
 System.Data.Odbc namespace to access the file using ODBC drivers.
</blockquote>

That would allow you to access your data via sql queries, as others proposed.

blocks|key|1929028|text|“此datatable是通过读取CSV文件而不是从DB创建的。”|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1929029|因此，在数据库中的四列上设置一个唯一的约束，并且在您的设计下重复的插入将不会进入。除非它决定失败，而不是在发生这种情况时继续执行，但这在CSV导入脚本中肯定是可配置的。|1929030|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

"This datatable is being created by reading a CSV file and not from a DB."

So put a unique constraint on the four columns in the database, and inserts that are duplicates under your design won't go in. Unless it decides to fail instead of continuing when this happens, but this surely is configurable in your CSV import script.

blocks|key|730915|text|这是一个非常简单的代码，它不需要linq或单个列来执行筛选。如果一行中所有列的值都为null，则将删除该值。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|730916|++++public+DataSet+duplicateRemoval(DataSet+dSet)+
{
++++bool+flag;
++++int+ccount+=+dSet.Tables[0].Columns.Count;
++++string[]+colst+=+new+string[ccount];
++++int+p+=+0;

++++DataSet+dsTemp+=+new+DataSet();
++++DataTable+Tables+=+new+DataTable();
++++dsTemp.Tables.Add(Tables);

++++for+(int+i+=+0;+i+<+ccount;+i%2B%2B)
++++{
++++++++dsTemp.Tables[0].Columns.Add(dSet.Tables[0].Columns[i].ColumnName,+System.Type.GetType("System.String"));
++++}

++++foreach+(System.Data.DataRow+row+in+dSet.Tables[0].Rows)
++++{
++++++++flag+=+false;
++++++++p+=+0;
++++++++foreach+(System.Data.DataColumn+col+in+dSet.Tables[0].Columns)
++++++++{
++++++++++++colst[p%2B%2B]+=+row[col].ToString();
++++++++++++if+(!string.IsNullOrEmpty(row[col].ToString()))
++++++++++++{++//Display+only+if+any+of+the+data+is+present+in+column
++++++++++++++++flag+=+true;
++++++++++++}
++++++++}
++++++++if+(flag+==+true)
++++++++{
++++++++++++DataRow+myRow+=+dsTemp.Tables[0].NewRow();
++++++++++++//Response.Write("<tr+style=\"background:#d2d2d2;\">");
++++++++++++for+(int+kk+=+0;+kk+<+ccount;+kk%2B%2B)
++++++++++++{
++++++++++++++++myRow[kk]+=+colst[kk];+++++++++

++++++++++++++++//+Response.Write("<td+class=\"table-line\"+bgcolor=\"#D2D2D2\">"+%2B+colst[kk]+%2B+"</td>");
++++++++++++}
++++++++++++dsTemp.Tables[0].Rows.Add(myRow);
++++++++}
++++}+return+dsTemp;
}|code-block|syntax|javascript|730917|这甚至可以用于从excel工作表中删除空数据。|730918|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

This is a very simple code which doesnot require linq nor individual columns to do the filter.
If all the values of columns in a row are null it will be deleted.

<hr>

<pre><code> public DataSet duplicateRemoval(DataSet dSet) 
{
 bool flag;
 int ccount = dSet.Tables[0].Columns.Count;
 string[] colst = new string[ccount];
 int p = 0;

 DataSet dsTemp = new DataSet();
 DataTable Tables = new DataTable();
 dsTemp.Tables.Add(Tables);

 for (int i = 0; i &lt; ccount; i++)
 {
 dsTemp.Tables[0].Columns.Add(dSet.Tables[0].Columns[i].ColumnName, System.Type.GetType("System.String"));
 }

 foreach (System.Data.DataRow row in dSet.Tables[0].Rows)
 {
 flag = false;
 p = 0;
 foreach (System.Data.DataColumn col in dSet.Tables[0].Columns)
 {
 colst[p++] = row[col].ToString();
 if (!string.IsNullOrEmpty(row[col].ToString()))
 { //Display only if any of the data is present in column
 flag = true;
 }
 }
 if (flag == true)
 {
 DataRow myRow = dsTemp.Tables[0].NewRow();
 //Response.Write("&lt;tr style=\"background:#d2d2d2;\"&gt;");
 for (int kk = 0; kk &lt; ccount; kk++)
 {
 myRow[kk] = colst[kk]; 

 // Response.Write("&lt;td class=\"table-line\" bgcolor=\"#D2D2D2\"&gt;" + colst[kk] + "&lt;/td&gt;");
 }
 dsTemp.Tables[0].Rows.Add(myRow);
 }
 } return dsTemp;
}
</code></pre>

<hr>

This can even be used to remove null data from excel sheet.

blocks|key|1929074|text|应该考虑到，必须调用Table.AcceptChanges()来完成删除。否则，已删除的行仍然存在于DataTable中，而RowState设置为已删除。删除后不改变Table.Rows.Count。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1929075|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

It should be taken into account that Table.AcceptChanges() must be called to complete the deletion. Otherwise deleted row is still present in DataTable with RowState set to Deleted. And Table.Rows.Count is not changed after deletion.

blocks|key|1929100|text|尝尝这个|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1929101|让我们考虑一下，dtInput是包含重复记录的数据表。|1929102|我有一个新的DataTable+dtFinal，在其中我要过滤重复的行。|1929103|所以我的代码如下所示。|1929104|DataTable+dtFinal+=+dtInput.DefaultView.ToTable(true,+
+++++++++++++++++++++++++++new+string[ColumnCount]+{"Col1Name","Col2Name","Col3Name",...,"ColnName"});|code-block|syntax|javascript|1929105|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Q|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|R|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|S|8|@]|9|@]|A|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Try this

Let us consider dtInput is your data table with duplicate records.

I have a new DataTable dtFinal in which I want to filter the duplicate rows.

So my code will be something like below.

<pre><code>DataTable dtFinal = dtInput.DefaultView.ToTable(true, 
 new string[ColumnCount] {"Col1Name","Col2Name","Col3Name",...,"ColnName"});
</code></pre>

blocks|key|730682|text|我并不热衷于使用上面的Linq解决方案，所以我写了如下：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|730683|///+<summary>
///+Takes+a+datatable+and+a+column+index,+and+returns+a+datatable+without+duplicates
///+</summary>
///+<param+name="dt">The+datatable+containing+duplicate+records</param>
///+<param+name="ComparisonFieldIndex">The+column+index+containing+duplicates</param>
///+<returns>A+datatable+object+without+duplicated+records</returns>
public+DataTable+duplicateRemoval(DataTable+dt,+int+ComparisonFieldIndex)
{
++++try
++++{
++++++++//Build+the+new+datatable+that+will+be+returned
++++++++DataTable+dtReturn+=+new+DataTable();
++++++++for+(int+i+=+0;+i+<+dt.Columns.Count;+i%2B%2B)
++++++++{
++++++++++++dtReturn.Columns.Add(dt.Columns[i].ColumnName,+System.Type.GetType("System.String"));
++++++++}

++++++++//Loop+through+each+record+in+the+datatable+we+have+been+passed
++++++++foreach+(DataRow+dr+in+dt.Rows)
++++++++{
++++++++++++bool+Found+=+false;
++++++++++++//Loop+through+each+record+already+present+in+the+datatable+being+returned
++++++++++++foreach+(DataRow+dr2+in+dtReturn.Rows)
++++++++++++{
++++++++++++++++bool+Identical+=+true;
++++++++++++++++//Compare+the+column+specified+to+see+if+it+matches+an+existing+record
++++++++++++++++if+(!(dr2[ComparisonFieldIndex].ToString()+==+dr[ComparisonFieldIndex].ToString()))
++++++++++++++++{
++++++++++++++++++++Identical+=+false;
++++++++++++++++}
++++++++++++++++//If+the+record+found+identically+matches+one+we+already+have,+don't+add+it+again
++++++++++++++++if+(Identical)
++++++++++++++++{
++++++++++++++++++++Found+=+true;
++++++++++++++++++++break;
++++++++++++++++}
++++++++++++}
++++++++++++//If+we+didn't+find+a+matching+record,+we'll+add+this+one
++++++++++++if+(!Found)
++++++++++++{
++++++++++++++++DataRow+drAdd+=+dtReturn.NewRow();
++++++++++++++++for+(int+i+=+0;+i+<+dtReturn.Columns.Count;+i%2B%2B)
++++++++++++++++{
++++++++++++++++++++drAdd[i]+=+dr[i];
++++++++++++++++}

++++++++++++++++dtReturn.Rows.Add(drAdd);
++++++++++++}
++++++++}
++++++++return+dtReturn;
++++}
++++catch+(Exception)
++++{
++++++++//Return+the+original+datatable+if+something+failed+above
++++++++return+dt;
++++}
}|code-block|syntax|javascript|730684|此外，这适用于所有列，而不是特定的列索引：|730685|///+<summary>
///+Takes+a+datatable+and+returns+a+datatable+without+duplicates
///+</summary>
///+<param+name="dt">The+datatable+containing+duplicate+records</param>
///+<returns>A+datatable+object+without+duplicated+records</returns>
public+DataTable+duplicateRemoval(DataTable+dt)
{
++++try
++++{
++++++++//Build+the+new+datatable+that+will+be+returned
++++++++DataTable+dtReturn+=+new+DataTable();
++++++++for+(int+i+=+0;+i+<+dt.Columns.Count;+i%2B%2B)
++++++++{
++++++++++++dtReturn.Columns.Add(dt.Columns[i].ColumnName,+System.Type.GetType("System.String"));
++++++++}

++++++++//Loop+through+each+record+in+the+datatable+we+have+been+passed
++++++++foreach+(DataRow+dr+in+dt.Rows)
++++++++{
++++++++++++bool+Found+=+false;
++++++++++++//Loop+through+each+record+already+present+in+the+datatable+being+returned
++++++++++++foreach+(DataRow+dr2+in+dtReturn.Rows)
++++++++++++{
++++++++++++++++bool+Identical+=+true;
++++++++++++++++//Compare+all+columns+to+see+if+they+match+the+existing+record
++++++++++++++++for+(int+i+=+0;+i+<+dt.Columns.Count;+i%2B%2B)
++++++++++++++++{
++++++++++++++++++++if+(!(dr2[i].ToString()+==+dr[i].ToString()))
++++++++++++++++++++{
++++++++++++++++++++++++Identical+=+false;
++++++++++++++++++++}
++++++++++++++++}
++++++++++++++++//If+the+record+found+identically+matches+one+we+already+have,+don't+add+it+again
++++++++++++++++if+(Identical)
++++++++++++++++{
++++++++++++++++++++Found+=+true;
++++++++++++++++++++break;
++++++++++++++++}
++++++++++++}
++++++++++++//If+we+didn't+find+a+matching+record,+we'll+add+this+one
++++++++++++if+(!Found)
++++++++++++{
++++++++++++++++DataRow+drAdd+=+dtReturn.NewRow();
++++++++++++++++for+(int+i+=+0;+i+<+dtReturn.Columns.Count;+i%2B%2B)
++++++++++++++++{
++++++++++++++++++++drAdd[i]+=+dr[i];
++++++++++++++++}

++++++++++++++++dtReturn.Rows.Add(drAdd);
++++++++++++}
++++++++}
++++++++return+dtReturn;
++++}
++++catch+(Exception)
++++{
++++++++//Return+the+original+datatable+if+something+failed+above
++++++++return+dt;
++++}
}|730686|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]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I wasn't keen on using the Linq solution above so I wrote this:

<pre><code>/// &lt;summary&gt;
/// Takes a datatable and a column index, and returns a datatable without duplicates
/// &lt;/summary&gt;
/// &lt;param name="dt"&gt;The datatable containing duplicate records&lt;/param&gt;
/// &lt;param name="ComparisonFieldIndex"&gt;The column index containing duplicates&lt;/param&gt;
/// &lt;returns&gt;A datatable object without duplicated records&lt;/returns&gt;
public DataTable duplicateRemoval(DataTable dt, int ComparisonFieldIndex)
{
 try
 {
 //Build the new datatable that will be returned
 DataTable dtReturn = new DataTable();
 for (int i = 0; i &lt; dt.Columns.Count; i++)
 {
 dtReturn.Columns.Add(dt.Columns[i].ColumnName, System.Type.GetType("System.String"));
 }

 //Loop through each record in the datatable we have been passed
 foreach (DataRow dr in dt.Rows)
 {
 bool Found = false;
 //Loop through each record already present in the datatable being returned
 foreach (DataRow dr2 in dtReturn.Rows)
 {
 bool Identical = true;
 //Compare the column specified to see if it matches an existing record
 if (!(dr2[ComparisonFieldIndex].ToString() == dr[ComparisonFieldIndex].ToString()))
 {
 Identical = false;
 }
 //If the record found identically matches one we already have, don't add it again
 if (Identical)
 {
 Found = true;
 break;
 }
 }
 //If we didn't find a matching record, we'll add this one
 if (!Found)
 {
 DataRow drAdd = dtReturn.NewRow();
 for (int i = 0; i &lt; dtReturn.Columns.Count; i++)
 {
 drAdd[i] = dr[i];
 }

 dtReturn.Rows.Add(drAdd);
 }
 }
 return dtReturn;
 }
 catch (Exception)
 {
 //Return the original datatable if something failed above
 return dt;
 }
}
</code></pre>

Additionally, this works on ALL columns rather than a specific column index:

<pre><code>/// &lt;summary&gt;
/// Takes a datatable and returns a datatable without duplicates
/// &lt;/summary&gt;
/// &lt;param name="dt"&gt;The datatable containing duplicate records&lt;/param&gt;
/// &lt;returns&gt;A datatable object without duplicated records&lt;/returns&gt;
public DataTable duplicateRemoval(DataTable dt)
{
 try
 {
 //Build the new datatable that will be returned
 DataTable dtReturn = new DataTable();
 for (int i = 0; i &lt; dt.Columns.Count; i++)
 {
 dtReturn.Columns.Add(dt.Columns[i].ColumnName, System.Type.GetType("System.String"));
 }

 //Loop through each record in the datatable we have been passed
 foreach (DataRow dr in dt.Rows)
 {
 bool Found = false;
 //Loop through each record already present in the datatable being returned
 foreach (DataRow dr2 in dtReturn.Rows)
 {
 bool Identical = true;
 //Compare all columns to see if they match the existing record
 for (int i = 0; i &lt; dt.Columns.Count; i++)
 {
 if (!(dr2[i].ToString() == dr[i].ToString()))
 {
 Identical = false;
 }
 }
 //If the record found identically matches one we already have, don't add it again
 if (Identical)
 {
 Found = true;
 break;
 }
 }
 //If we didn't find a matching record, we'll add this one
 if (!Found)
 {
 DataRow drAdd = dtReturn.NewRow();
 for (int i = 0; i &lt; dtReturn.Columns.Count; i++)
 {
 drAdd[i] = dr[i];
 }

 dtReturn.Rows.Add(drAdd);
 }
 }
 return dtReturn;
 }
 catch (Exception)
 {
 //Return the original datatable if something failed above
 return dt;
 }
}
</code></pre>

blocks|key|1929159|text|我认为这一定是使用和moreLinq代码从Linq+Datatable中删除重复项的最佳方法：|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|CODE|entityRanges|data|1929160|Linq|1929161|RemoveDuplicatesRecords(yourDataTable);


private+DataTable+RemoveDuplicatesRecords(DataTable+dt)
{
++++var+UniqueRows+=+dt.AsEnumerable().Distinct(DataRowComparer.Default);
++++DataTable+dt2+=+UniqueRows.CopyToDataTable();
++++return+dt2;
}|code-block|syntax|javascript|1929162|MoreLinq|1929163|//+Distinctby++column+name+ID+
var+valueDistinctByIdColumn+=+yourTable.AsEnumerable().DistinctBy(row+=>+new+{+Id+=+row["Id"]+});
DataTable+dtDistinctByIdColumn+=+valueDistinctByIdColumn.CopyToDataTable();|1929164|注意：moreLinq需要添加库。|1929165|在morelinq中，您可以使用名为DistinctBy的函数，其中可以指定要在其中查找不同对象的属性。|1929166|entityMap^0|9|Q|A|8|L|4|0|0|4|0|0|0|0|3|8|0|1|8|0^^$0|@$1|2|3|4|5|6|7|X|8|@$9|Y|A|Z|B|C]|$9|10|A|11|B|D]|$9|12|A|13|B|D]]|E|@]|F|$]]|$1|G|3|H|5|6|7|14|8|@$9|15|A|16|B|C]]|E|@]|F|$]]|$1|I|3|J|5|K|7|17|8|@]|E|@]|F|$L|M]]|$1|N|3|O|5|6|7|18|8|@]|E|@]|F|$]]|$1|P|3|Q|5|K|7|19|8|@]|E|@]|F|$L|M]]|$1|R|3|S|5|6|7|1A|8|@$9|1B|A|1C|B|D]]|E|@]|F|$]]|$1|T|3|U|5|6|7|1D|8|@$9|1E|A|1F|B|C]]|E|@]|F|$]]|$1|V|3|-4|5|6|7|1G|8|@]|E|@]|F|$]]]|W|$]]

I think this must be the best way to remove duplicates from Datatable by using <code>Linq</code> and <code>moreLinq</code>
Code:
Linq
<pre><code>RemoveDuplicatesRecords(yourDataTable);


private DataTable RemoveDuplicatesRecords(DataTable dt)
{
 var UniqueRows = dt.AsEnumerable().Distinct(DataRowComparer.Default);
 DataTable dt2 = UniqueRows.CopyToDataTable();
 return dt2;
}
</code></pre>
<hr />
<h2>MoreLinq</h2>
<pre><code>// Distinctby column name ID 
var valueDistinctByIdColumn = yourTable.AsEnumerable().DistinctBy(row =&gt; new { Id = row[&quot;Id&quot;] });
DataTable dtDistinctByIdColumn = valueDistinctByIdColumn.CopyToDataTable();
 
</code></pre>
Note: <code>moreLinq</code> need to add library.
In morelinq you can use function called DistinctBy in which you can specify the property on which you want to find Distinct objects.

I have checked the whole site and googled on the net but was unable to find a simple solution to this problem.

I have a datatable which has about 20 columns and 10K rows. I need to remove the duplicate rows in this datatable based on 4 key columns. Doesn't .Net have a function which does this? The function closest to what I am looking for was datatable.DefaultView.ToTable(true, array of columns to display), But this function does a distinct on all the columns.

It would be great if someone could help me with this.

EDIT: I am sorry for not being clear on this. This datatable is being created by reading a CSV file and not from a DB. So using an SQL query is not an option.

What is the best way to remove duplicates from a datatable?

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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我已经检查了整个网站，并在网上搜索，但没有找到一个简单的解决方案，这个问题。我有一个datatable，它有大约20列和10K行。我需要根据4个键列删除datatable中重复的行。.Net没有这样的函数吗？与我所寻找的最接近的函数是datatable.DefaultView.ToTable(是的，要显示的列数组)，但...

问从datatable中删除重复项的最佳方法是什么？
EN

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问从datatable中删除重复项的最佳方法是什么？EN