2.5倍比其他正则表达式方法更快和最有效的方法:

/// <summary>
/// Returns a new string in which all occurrences of a specified string in the current instance are replaced with another 
/// specified string according the type of search to use for the specified string.
/// </summary>
/// <param name="str">The string performing the replace method.</param>
/// <param name="oldValue">The string to be replaced.</param>
/// <param name="newValue">The string replace all occurrences of <paramref name="oldValue"/>. 
/// If value is equal to <c>null</c>, than all occurrences of <paramref name="oldValue"/> will be removed from the <paramref name="str"/>.</param>
/// <param name="comparisonType">One of the enumeration values that specifies the rules for the search.</param>
/// <returns>A string that is equivalent to the current string except that all instances of <paramref name="oldValue"/> are replaced with <paramref name="newValue"/>. 
/// If <paramref name="oldValue"/> is not found in the current instance, the method returns the current instance unchanged.</returns>
[DebuggerStepThrough]
public static string Replace(this string str,
    string oldValue, string newValue,
    StringComparison comparisonType)
{

    // Check inputs.
    if (str == null)
    {
        // Same as original .NET C# string.Replace behavior.
        throw new ArgumentNullException(nameof(str));
    }
    if (str.Length == 0)
    {
        // Same as original .NET C# string.Replace behavior.
        return str;
    }
    if (oldValue == null)
    {
        // Same as original .NET C# string.Replace behavior.
        throw new ArgumentNullException(nameof(oldValue));
    }
    if (oldValue.Length == 0)
    {
        // Same as original .NET C# string.Replace behavior.
        throw new ArgumentException("String cannot be of zero length.");
    }
    

    //if (oldValue.Equals(newValue, comparisonType))
    //{
    //This condition has no sense
    //It will prevent method from replacesing: "Example", "ExAmPlE", "EXAMPLE" to "example"
    //return str;
    //}



    // Prepare string builder for storing the processed string.
    // Note: StringBuilder has a better performance than String by 30-40%.
    StringBuilder resultStringBuilder = new StringBuilder(str.Length);



    // Analyze the replacement: replace or remove.
    bool isReplacementNullOrEmpty = string.IsNullOrEmpty(newValue);



    // Replace all values.
    const int valueNotFound = -1;
    int foundAt;
    int startSearchFromIndex = 0;
    while ((foundAt = str.IndexOf(oldValue, startSearchFromIndex, comparisonType)) != valueNotFound)
    {
        
        // Append all characters until the found replacement.
        int charsUntilReplacment = foundAt - startSearchFromIndex;
        bool isNothingToAppend = charsUntilReplacment == 0;
        if (!isNothingToAppend)
        {
            resultStringBuilder.Append(str, startSearchFromIndex, charsUntilReplacment);
        }
        


        // Process the replacement.
        if (!isReplacementNullOrEmpty)
        {
            resultStringBuilder.Append(newValue);
        }
        

        // Prepare start index for the next search.
        // This needed to prevent infinite loop, otherwise method always start search 
        // from the start of the string. For example: if an oldValue == "EXAMPLE", newValue == "example"
        // and comparisonType == "any ignore case" will conquer to replacing:
        // "EXAMPLE" to "example" to "example" to "example" … infinite loop.
        startSearchFromIndex = foundAt + oldValue.Length;
        if (startSearchFromIndex == str.Length)
        {
            // It is end of the input string: no more space for the next search.
            // The input string ends with a value that has already been replaced. 
            // Therefore, the string builder with the result is complete and no further action is required.
            return resultStringBuilder.ToString();
        }
    }
    

    // Append the last part to the result.
    int charsUntilStringEnd = str.Length - startSearchFromIndex;
    resultStringBuilder.Append(str, startSearchFromIndex, charsUntilStringEnd);


    return resultStringBuilder.ToString();

}

注意:忽略case == StringComparison。OrdinalIgnoreCase作为stringcomparisontype的参数。它是替换所有值的最快、不区分大小写的方法。

该方法的优点:

High CPU and MEMORY efficiency; It is the fastest solution, 2.5 times faster than other's methods with regular expressions (proof in the end); Suitable for removing parts from the input string (set newValue to null), optimized for this; Same as original .NET C# string.Replace behavior, same exceptions; Well commented, easy to understand; Simpler – no regular expressions. Regular expressions are always slower because of their versatility (even compiled); This method is well tested and there are no hidden flaws like infinite loop in other's solutions, even highly rated:

@AsValeO: Not适用于Regex语言元素，所以它不是 普遍的方法

这段代码有问题。如果文本为new 是文本的超集，这样可以产生无限循环。

防基准测试:这个解决方案比@Steve B.的regex快2.59倍，代码:

// Results:
// 1/2. Regular expression solution: 4486 milliseconds
// 2/2. Current solution: 1727 milliseconds — 2.59X times FASTER! than regex!

// Notes: the test was started 5 times, the result is an average; release build.

const int benchmarkIterations = 1000000;
const string sourceString = "aaaaddsdsdsdsdsd";
const string oldValue = "D";
const string newValue = "Fod";
long totalLenght = 0;

Stopwatch regexStopwatch = Stopwatch.StartNew();
string tempString1;
for (int i = 0; i < benchmarkIterations; i++)
{
    tempString1 = sourceString;
    tempString1 = ReplaceCaseInsensitive(tempString1, oldValue, newValue);

    totalLenght = totalLenght + tempString1.Length;
}
regexStopwatch.Stop();



Stopwatch currentSolutionStopwatch = Stopwatch.StartNew();
string tempString2;
for (int i = 0; i < benchmarkIterations; i++)
{
    tempString2 = sourceString;
    tempString2 = tempString2.Replace(oldValue, newValue,
        StringComparison.OrdinalIgnoreCase);

    totalLenght = totalLenght + tempString2.Length;
}
currentSolutionStopwatch.Stop();

原创创意- @Darky711;感谢@ miner的StringBuilder。

您还可以尝试Regex类。

var regex = new regex ("camel"， RegexOptions. var regex = new regex。IgnoreCase); var newSentence =正则表达式。替换(句子，“马”);

2.5倍比其他正则表达式方法更快和最有效的方法:

/// <summary>
/// Returns a new string in which all occurrences of a specified string in the current instance are replaced with another 
/// specified string according the type of search to use for the specified string.
/// </summary>
/// <param name="str">The string performing the replace method.</param>
/// <param name="oldValue">The string to be replaced.</param>
/// <param name="newValue">The string replace all occurrences of <paramref name="oldValue"/>. 
/// If value is equal to <c>null</c>, than all occurrences of <paramref name="oldValue"/> will be removed from the <paramref name="str"/>.</param>
/// <param name="comparisonType">One of the enumeration values that specifies the rules for the search.</param>
/// <returns>A string that is equivalent to the current string except that all instances of <paramref name="oldValue"/> are replaced with <paramref name="newValue"/>. 
/// If <paramref name="oldValue"/> is not found in the current instance, the method returns the current instance unchanged.</returns>
[DebuggerStepThrough]
public static string Replace(this string str,
    string oldValue, string newValue,
    StringComparison comparisonType)
{

    // Check inputs.
    if (str == null)
    {
        // Same as original .NET C# string.Replace behavior.
        throw new ArgumentNullException(nameof(str));
    }
    if (str.Length == 0)
    {
        // Same as original .NET C# string.Replace behavior.
        return str;
    }
    if (oldValue == null)
    {
        // Same as original .NET C# string.Replace behavior.
        throw new ArgumentNullException(nameof(oldValue));
    }
    if (oldValue.Length == 0)
    {
        // Same as original .NET C# string.Replace behavior.
        throw new ArgumentException("String cannot be of zero length.");
    }
    

    //if (oldValue.Equals(newValue, comparisonType))
    //{
    //This condition has no sense
    //It will prevent method from replacesing: "Example", "ExAmPlE", "EXAMPLE" to "example"
    //return str;
    //}



    // Prepare string builder for storing the processed string.
    // Note: StringBuilder has a better performance than String by 30-40%.
    StringBuilder resultStringBuilder = new StringBuilder(str.Length);



    // Analyze the replacement: replace or remove.
    bool isReplacementNullOrEmpty = string.IsNullOrEmpty(newValue);



    // Replace all values.
    const int valueNotFound = -1;
    int foundAt;
    int startSearchFromIndex = 0;
    while ((foundAt = str.IndexOf(oldValue, startSearchFromIndex, comparisonType)) != valueNotFound)
    {
        
        // Append all characters until the found replacement.
        int charsUntilReplacment = foundAt - startSearchFromIndex;
        bool isNothingToAppend = charsUntilReplacment == 0;
        if (!isNothingToAppend)
        {
            resultStringBuilder.Append(str, startSearchFromIndex, charsUntilReplacment);
        }
        


        // Process the replacement.
        if (!isReplacementNullOrEmpty)
        {
            resultStringBuilder.Append(newValue);
        }
        

        // Prepare start index for the next search.
        // This needed to prevent infinite loop, otherwise method always start search 
        // from the start of the string. For example: if an oldValue == "EXAMPLE", newValue == "example"
        // and comparisonType == "any ignore case" will conquer to replacing:
        // "EXAMPLE" to "example" to "example" to "example" … infinite loop.
        startSearchFromIndex = foundAt + oldValue.Length;
        if (startSearchFromIndex == str.Length)
        {
            // It is end of the input string: no more space for the next search.
            // The input string ends with a value that has already been replaced. 
            // Therefore, the string builder with the result is complete and no further action is required.
            return resultStringBuilder.ToString();
        }
    }
    

    // Append the last part to the result.
    int charsUntilStringEnd = str.Length - startSearchFromIndex;
    resultStringBuilder.Append(str, startSearchFromIndex, charsUntilStringEnd);


    return resultStringBuilder.ToString();

}

注意:忽略case == StringComparison。OrdinalIgnoreCase作为stringcomparisontype的参数。它是替换所有值的最快、不区分大小写的方法。

该方法的优点:

High CPU and MEMORY efficiency; It is the fastest solution, 2.5 times faster than other's methods with regular expressions (proof in the end); Suitable for removing parts from the input string (set newValue to null), optimized for this; Same as original .NET C# string.Replace behavior, same exceptions; Well commented, easy to understand; Simpler – no regular expressions. Regular expressions are always slower because of their versatility (even compiled); This method is well tested and there are no hidden flaws like infinite loop in other's solutions, even highly rated:

@AsValeO: Not适用于Regex语言元素，所以它不是 普遍的方法

这段代码有问题。如果文本为new 是文本的超集，这样可以产生无限循环。

防基准测试:这个解决方案比@Steve B.的regex快2.59倍，代码:

// Results:
// 1/2. Regular expression solution: 4486 milliseconds
// 2/2. Current solution: 1727 milliseconds — 2.59X times FASTER! than regex!

// Notes: the test was started 5 times, the result is an average; release build.

const int benchmarkIterations = 1000000;
const string sourceString = "aaaaddsdsdsdsdsd";
const string oldValue = "D";
const string newValue = "Fod";
long totalLenght = 0;

Stopwatch regexStopwatch = Stopwatch.StartNew();
string tempString1;
for (int i = 0; i < benchmarkIterations; i++)
{
    tempString1 = sourceString;
    tempString1 = ReplaceCaseInsensitive(tempString1, oldValue, newValue);

    totalLenght = totalLenght + tempString1.Length;
}
regexStopwatch.Stop();



Stopwatch currentSolutionStopwatch = Stopwatch.StartNew();
string tempString2;
for (int i = 0; i < benchmarkIterations; i++)
{
    tempString2 = sourceString;
    tempString2 = tempString2.Replace(oldValue, newValue,
        StringComparison.OrdinalIgnoreCase);

    totalLenght = totalLenght + tempString2.Length;
}
currentSolutionStopwatch.Stop();

原创创意- @Darky711;感谢@ miner的StringBuilder。

你可以使用Regex并执行不区分大小写的替换:

class Program
{
    static void Main()
    {
        string input = "hello WoRlD";
        string result = 
           Regex.Replace(input, "world", "csharp", RegexOptions.IgnoreCase);
        Console.WriteLine(result); // prints "hello csharp"
    }
}

(编辑:没有意识到“裸链接”的问题，对不起)

从这里开始:

string myString = "find Me and replace ME";
string strReplace = "me";
myString = Regex.Replace(myString, "me", strReplace, RegexOptions.IgnoreCase);

似乎你不是第一个抱怨字符串不区分大小写的人。

很多使用Regex的建议。如果没有它，这个扩展方法如何:

public static string Replace(this string str, string old, string @new, StringComparison comparison)
{
    @new = @new ?? "";
    if (string.IsNullOrEmpty(str) || string.IsNullOrEmpty(old) || old.Equals(@new, comparison))
        return str;
    int foundAt = 0;
    while ((foundAt = str.IndexOf(old, foundAt, comparison)) != -1)
    {
        str = str.Remove(foundAt, old.Length).Insert(foundAt, @new);
        foundAt += @new.Length;
    }
    return str;
}