blocks|key|1312918|text|Substring中的第二个参数是子字符串的长度，而不是结束索引。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1312919|您可能应该包括处理，以检查它是否确实以您期望的内容开始，以您期望的内容结束，并且至少与您期望的一样长。如果不匹配，您可以执行其他操作或抛出有意义的错误。|1312920|下面是一些示例代码，用于验证url是否包含您的字符串，这些代码也进行了一些重构，以便更容易地将前缀/后缀更改为strip：|1312921|var+prefix+=+"www.example.com/";
var+suffix+=+".jpg";
string+url+=+"www.example.com/aaa/bbb.jpg";

if+(url.StartsWith(prefix)+&&+url.EndsWith(suffix)+&&+url.Length+>=+(prefix.Length+%2B+suffix.Length))
{
++++string+newString+=+url.Substring(prefix.Length,+url.Length+-+prefix.Length+-+suffix.Length);
++++Console.WriteLine(newString);
}
else
++++//handle+invalid+state|code-block|syntax|javascript|1312922|entityMap|0|LINK|mutability|MUTABLE|url|https://msdn.microsoft.com/en-us/library/aka44szs(v=vs.110).aspx^0|0|9|0|9|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|F|3|G|5|6|7|12|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|13|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|14|8|@]|D|@]|E|$M|N]]|$1|O|3|-4|5|6|7|15|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]]]

The second parameter in <a href="https://msdn.microsoft.com/en-us/library/aka44szs(v=vs.110).aspx" rel="noreferrer"><code>Substring</code></a> is the length of the substring, not the end index.

You should probably include handling to check that it does indeed start with what you expect, end with what you expect, and is at least as long as you expect. And then if it doesn't match, you can either do something else or throw a meaningful error.

Here's some example code that validates that url contains your strings, that also is refactored a bit to make it easier to change the prefix/suffix to strip:

<pre><code>var prefix = "www.example.com/";
var suffix = ".jpg";
string url = "www.example.com/aaa/bbb.jpg";

if (url.StartsWith(prefix) &amp;&amp; url.EndsWith(suffix) &amp;&amp; url.Length &gt;= (prefix.Length + suffix.Length))
{
 string newString = url.Substring(prefix.Length, url.Length - prefix.Length - suffix.Length);
 Console.WriteLine(newString);
}
else
 //handle invalid state
</code></pre>

blocks|key|2948722|text|您的错误是子字符串的参数。第一个参数应该是起始索引，第二个参数应该是起始索引的长度或偏移量。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2948723|string+newString+=+url.Substring(18,+7);|code-block|syntax|javascript|2948724|如果子字符串的长度可以变化，则需要计算长度。|2948725|在(url.Length+-+18)+-+4+(或url.Length+-+22)方向上的一些东西|offset|length|style|CODE|2948726|最后，它将看起来像这样|2948727|string+newString+=+url.Substring(18,+url.Length+-+22);|2948728|entityMap^0|0|0|0|1|L|P|F|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|X|8|@$K|Y|L|Z|M|N]|$K|10|L|11|M|N]]|9|@]|A|$]]|$1|O|3|P|5|6|7|12|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|S|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|T|$]]

Your mistake is the parameters to Substring. The first parameter should be the start index and the second should be the length or offset from the startindex.

<pre><code>string newString = url.Substring(18, 7);
</code></pre>

If the length of the substring can vary you need to calculate the length.

Something in the direction of <code>(url.Length - 18) - 4</code> (or <code>url.Length - 22</code>) 

In the end it will look something like this

<pre><code>string newString = url.Substring(18, url.Length - 22);
</code></pre>

blocks|key|2948747|text|试试这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2948748|+int+positionOfJPG=url.IndexOf(".jpg");
+string+newString+=+url.Substring(18,+url.Length+-+positionOfJPG);|code-block|syntax|javascript|2948749|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|$]]

Try This:

<pre><code> int positionOfJPG=url.IndexOf(".jpg");
 string newString = url.Substring(18, url.Length - positionOfJPG);
</code></pre>

blocks|key|2948790|text|您需要找到第一个/的位置，然后计算您想要的部分：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2948791|string+url+=+"www.example.com/aaa/bbb.jpg";
int+Idx+=+url.IndexOf("/");
string+yourValue+=+url.Substring(Idx+%2B+1,+url.Length+-+Idx+-+4);|code-block|syntax|javascript|2948792|entityMap^0|8|1|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

You need to find the position of the first <code>/</code>, and then calculate the portion you want:

<pre><code>string url = "www.example.com/aaa/bbb.jpg";
int Idx = url.IndexOf("/");
string yourValue = url.Substring(Idx + 1, url.Length - Idx - 4);
</code></pre>

blocks|key|3036916|text|string+newString+=+url.Substring(18,+(url.LastIndexOf(".")+-+18))|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|3036917|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>string newString = url.Substring(18, (url.LastIndexOf(".") - 18))
</code></pre>

blocks|key|1709011|text|这是另一个建议。如果您可以在url字符串前面加上http://，就可以做到这一点|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1709012|++string+path+=+"http://www.example.com/aaa/bbb.jpg";
++Uri+uri+=+new+Uri(path);++++++++++++
++string+expectedString+=+
++++++uri.PathAndQuery.Remove(uri.PathAndQuery.LastIndexOf("."));|code-block|syntax|javascript|1709013|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|$]]

Here is another suggestion. If you can prepend http:// to your url string you can do this

<pre><code> string path = "http://www.example.com/aaa/bbb.jpg";
 Uri uri = new Uri(path); 
 string expectedString = 
 uri.PathAndQuery.Remove(uri.PathAndQuery.LastIndexOf("."));
</code></pre>

blocks|key|3036935|text|这样如何：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3036936|string+url+=+"http://www.example.com/aaa/bbb.jpg";
Uri+uri+=+new+Uri(url);
string+path_Query+=+uri.PathAndQuery;
string+extension+=++Path.GetExtension(path_Query);

path_Query+=+path_Query.Replace(extension,+string.Empty);//+This+will+remove+extension|code-block|syntax|javascript|3036937|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|$]]

How about something like this :

<pre><code>string url = "http://www.example.com/aaa/bbb.jpg";
Uri uri = new Uri(url);
string path_Query = uri.PathAndQuery;
string extension = Path.GetExtension(path_Query);

path_Query = path_Query.Replace(extension, string.Empty);// This will remove extension
</code></pre>

blocks|key|1313119|text|你需要像这样检查你的语句：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1313120|string+url+=+"www.example.com/aaa/bbb.jpg";
string+lenght+=+url.Lenght-4;
if(url.Lenght+>+15)//eg+15
{
+string+newString+=+url.Substring(18,+lenght);
}|code-block|syntax|javascript|1313121|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|$]]

You need to check your statement like this :
<pre><code>string url = &quot;www.example.com/aaa/bbb.jpg&quot;;
string lenght = url.Lenght-4;
if(url.Lenght &gt; 15)//eg 15
{
 string newString = url.Substring(18, lenght);
}
</code></pre>

I have a string that looks like 

<pre><code>string url = "www.example.com/aaa/bbb.jpg";
</code></pre>

"www.example.com/" is 18 fixed in length. I want to get the "aaa/bbb" part from this string (The actual url is not example nor aaa/bbb though, the length may vary)

so here's what I did:

<pre><code>string newString = url.Substring(18, url.Length - 4);
</code></pre>

Then I got the exception: index and length must refer to a location within the string. What's wrong with my code and how to fix it? Thanks in advance.

Substring index and length must refer to a location within the string

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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我有一个字符串，看起来像这样string url = "www.example.com/aaa/bbb.jpg";"www.example.com/“的长度固定为18。我想从这个字符串中获取" aaa/bbb“部分(实际的url既不是example也不是aaa/bbb，但长度可能会有所不同)下面是我所做的：string...

问子字符串索引和长度必须引用字符串中的某个位置
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