C#中的Replace函式返回的是替換後的新的字串，所以還需要在賦值一次。

String s="abcd";

s= s.Replace("a","e");

這樣就可以了，先搞清楚daoreplace的用法，明白引數的順序

using System;

publicclass ReplaceTest {

publicstaticvoid Main() {

string errString = "This docment uses 3 other docments to docment the docmentation";

Console.WriteLine("The original string is:{0}"{1}"{0}", Environment.NewLine, errString);

// Correct the spelling of "document".

string correctString = errString.Replace("docment", "document");

Console.WriteLine("After correcting the string, the result is:{0}"{1}"",

Environment.NewLine, correctString);

}

}

//

// This code example produces the following output:

//

// The original string is:

// "This docment uses 3 other docments to docment the docmentation"

//

// After correcting the string, the result is:

// "This document uses 3 other documents to document the documentation"