以下应能起作用:

the following should work:

string strng = "dsksf#dfkfdsafl#dsfksa";
var s = strng.Substring(strng.IndexOf("#") + 1, strng.LastIndexOf("#") - strng.IndexOf("#") - 1);
var sw = new StreamWriter(@"C:\Users\clifford\Documents\text.txt");
sw.Write(s);
sw.Close();

在这里，我假设您要存储字符串，而不是保存字符串，如果要打开文本文件来获取字符串，可以使用以下命令:

Here I am assuming you want to store the string, not save the string, if you want to open a text file to get the string you can use the following:

var sr = new StreamReader(@"C:\Users\clifford\Documents\text.txt");
var x = sr.ReadToEnd();
sr.Close();

小心点，将其存储在磁盘上.

Be careful with your words, store would be to disk.

使用String.IndexOf函数获取#字符的位置.
使用String.LastIndexOf函数获取最后#个字符的位置.
然后，只需使用String.SubString 方法 [

Use the String.IndexOf function to get location of the # character.
Use the String.LastIndexOf function to get location of the last # character.
Then, just use String.SubString method[^] to get the characters in the middle set.

Clifford的字符串切片答案还有另一种解决方案.您可以使用Regex来执行此操作.
正则表达式非常强大，非常适合字符串操作.

在您的情况下，您可以这样操作:

Hi,

There''s an alternative solution to Clifford''s string slicing answer. You could use Regex to do this.
Regex is very powerful and is a very well suited at string manipulation.

In your case you could do it like this:

string strng = "dsksf#dfkfdsafl#dsfksa";
Match match = Regex.Match(strng, "#.*#");
string result = match.Value.Substring(1, match.Value.Length - 2);

正则表达式上有很多可用资源:
http://msdn.microsoft.com/en-us/library/c75he57e.aspx [ ^ ]
http://www.regular-expressions.info/ [ http://www.pagecolumn.com/tool/regtest.htm [

There are plenty on resources on Regex available:
http://msdn.microsoft.com/en-us/library/c75he57e.aspx[^]
http://www.regular-expressions.info/[^]

There are also a few online regex testers:
http://www.pagecolumn.com/tool/regtest.htm[^]

Valery.