我更喜欢这个- "Hello World". tolower()。Replace("world"， " chsharp ");

.Net Core有这个内置的方法: 替换(String, String, StringComparison) Doc。现在我们可以简单地写: “…”。替换("oldValue"， "newValue"， stringcompare . ordinalignorecase)

扩展让我们的生活更简单:

static public class StringExtensions
{
    static public string ReplaceInsensitive(this string str, string from, string to)
    {
        str = Regex.Replace(str, from, to, RegexOptions.IgnoreCase);
        return str;
    }
}

另一种方法是使用StringComparison选项忽略String.Replace()中的大小写敏感性。CurrentCultureIgnoreCase

string.Replace("World", "csharp", StringComparison.CurrentCultureIgnoreCase)

使用这个，测试和100%工作!

VB。网

Dim myString As String
Dim oldValue As String
Dim newValue As String

myString = Form1.TextBox1.Text
oldValue = TextBox1.Text
newValue = TextBox2.Text

Dim working As String = myString
Dim index As Integer = working.IndexOf(oldValue, StringComparison.CurrentCultureIgnoreCase)

While index <> -1
    working = working.Remove(index, oldValue.Length)
    working = working.Insert(index, newValue)
    index = index + newValue.Length
    index = working.IndexOf(oldValue, index, StringComparison.CurrentCultureIgnoreCase)
    Form1.TextBox1.Text = working
End While

为c#

private void Button2_Click(System.Object sender, System.EventArgs e)
{
    string myString;
    string oldValue;
    string newValue;

    myString = Form1.TextBox1.Text;
    oldValue = TextBox1.Text;
    newValue = TextBox2.Text;

    string working = myString;
    int index = working.IndexOf(oldValue, StringComparison.CurrentCultureIgnoreCase);

    while (index != -1)
    {
        working = working.Remove(index, oldValue.Length);
        working = working.Insert(index, newValue);
        index = index + newValue.Length;
        index = working.IndexOf(oldValue, index, StringComparison.CurrentCultureIgnoreCase);
        Form1.TextBox1.Text = working;
    }
}

var search = "world";
var replacement = "csharp";
string result = Regex.Replace(
    stringToLookInto,
    Regex.Escape(search), 
    replacement.Replace("$","$$"), 
    RegexOptions.IgnoreCase
);

正则表达式。如果您依赖于可能包含Regex语言元素的用户输入，那么Escape是有用的

更新

多亏了注释，您实际上不必转义替换字符串。

下面是一个测试代码的小工具:

using System;
using System.Text.RegularExpressions;           
public class Program
{
    public static void Main()
    {

        var tests = new[] {
            new { Input="abcdef", Search="abc", Replacement="xyz", Expected="xyzdef" },
            new { Input="ABCdef", Search="abc", Replacement="xyz", Expected="xyzdef" },
            new { Input="A*BCdef", Search="a*bc", Replacement="xyz", Expected="xyzdef" },
            new { Input="abcdef", Search="abc", Replacement="x*yz", Expected="x*yzdef" },       
            new { Input="abcdef", Search="abc", Replacement="$", Expected="$def" },
        };


        foreach(var test in tests){
            var result = ReplaceCaseInsensitive(test.Input, test.Search, test.Replacement);

            Console.WriteLine(
                "Success: {0}, Actual: {1}, {2}",
                result == test.Expected,
                result,
                test
            );

        }


    }

    private static string ReplaceCaseInsensitive(string input, string search, string replacement){
        string result = Regex.Replace(
            input,
            Regex.Escape(search), 
            replacement.Replace("$","$$"), 
            RegexOptions.IgnoreCase
        );
        return result;
    }
}

它的输出是:

Success: True, Actual: xyzdef, { Input = abcdef, Search = abc, Replacement = xyz, Expected = xyzdef } 
Success: True, Actual: xyzdef, { Input = ABCdef, Search = abc, Replacement = xyz, Expected = xyzdef }
Success: True, Actual: xyzdef, { Input = A*BCdef, Search = a*bc, Replacement = xyz, Expected = xyzdef } 
Success: True, Actual: x*yzdef, { Input = abcdef, Search = abc, Replacement = x*yz, Expected = x*yzdef} 
Success: True, Actual: $def, { Input = abcdef, Search = abc, Replacement = $, Expected = $def }