I had to do something similar for work, but in my case I had to filter all that is not a letter, number or whitespace (but you could easily modify it to your needs). The filtering is done client-side in JavaScript, but for security reasons I am also doing the filtering server-side. Since I can expect most of the strings to be clean, I would like to avoid copying the string unless I really need to. This let my to the implementation below, which should perform better for both clean and dirty strings.

public static string EnsureOnlyLetterDigitOrWhiteSpace(string input)
{
    StringBuilder cleanedInput = null;
    for (var i = 0; i < input.Length; ++i)
    {
        var currentChar = input[i];
        var charIsValid = char.IsLetterOrDigit(currentChar) || char.IsWhiteSpace(currentChar);

        if (charIsValid)
        {
            if(cleanedInput != null)
                cleanedInput.Append(currentChar);
        }
        else
        {
            if (cleanedInput != null) continue;
            cleanedInput = new StringBuilder();
            if (i > 0)
                cleanedInput.Append(input.Substring(0, i));
        }
    }

    return cleanedInput == null ? input : cleanedInput.ToString();
}

I had to do something similar for work, but in my case I had to filter all that is not a letter, number or whitespace (but you could easily modify it to your needs). The filtering is done client-side in JavaScript, but for security reasons I am also doing the filtering server-side. Since I can expect most of the strings to be clean, I would like to avoid copying the string unless I really need to. This let my to the implementation below, which should perform better for both clean and dirty strings.

public static string EnsureOnlyLetterDigitOrWhiteSpace(string input)
{
    StringBuilder cleanedInput = null;
    for (var i = 0; i < input.Length; ++i)
    {
        var currentChar = input[i];
        var charIsValid = char.IsLetterOrDigit(currentChar) || char.IsWhiteSpace(currentChar);

        if (charIsValid)
        {
            if(cleanedInput != null)
                cleanedInput.Append(currentChar);
        }
        else
        {
            if (cleanedInput != null) continue;
            cleanedInput = new StringBuilder();
            if (i > 0)
                cleanedInput.Append(input.Substring(0, i));
        }
    }

    return cleanedInput == null ? input : cleanedInput.ToString();
}

我将使用字符串替换为正则表达式搜索“特殊字符”，替换所有字符找到一个空字符串。

如果你使用的是动态字符列表，LINQ可以提供一个更快更优雅的解决方案:

public static string RemoveSpecialCharacters(string value, char[] specialCharacters)
{
    return new String(value.Except(specialCharacters).ToArray());
}

我将这种方法与之前的两种“快速”方法(发行版编译)进行了比较:

字符数组解决方案由LukeH - 427毫秒 StringBuilder解决方案- 429毫秒 LINQ(这个答案)- 98毫秒

注意，算法略有修改-字符作为数组传入，而不是硬编码，这可能会有轻微的影响(即/其他解决方案将有一个内部for循环来检查字符数组)。

如果我使用LINQ where子句切换到硬编码的解决方案，结果是:

字符数组解决方案- 7ms StringBuilder解决方案- 22ms LINQ - 60毫秒

如果您计划编写一个更通用的解决方案，而不是硬编码字符列表，那么可能值得考虑LINQ或经过修改的方法。LINQ绝对能给你简洁、高可读性的代码——甚至比Regex更好。

public static string RemoveSpecialCharacters(string str)
{
    char[] buffer = new char[str.Length];
    int idx = 0;

    foreach (char c in str)
    {
        if ((c >= '0' && c <= '9') || (c >= 'A' && c <= 'Z')
            || (c >= 'a' && c <= 'z') || (c == '.') || (c == '_'))
        {
            buffer[idx] = c;
            idx++;
        }
    }

    return new string(buffer, 0, idx);
}

我同意这个代码示例。唯一不同的是，我把它变成字符串类型的扩展方法。所以你可以在非常简单的一行或代码中使用它:

string test = "abc@#$123";
test.RemoveSpecialCharacters();

感谢Guffa的实验。

public static class MethodExtensionHelper
    {
    public static string RemoveSpecialCharacters(this string str)
        {
            StringBuilder sb = new StringBuilder();
            foreach (char c in str)
            {
                if ((c >= '0' && c <= '9') || (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || c == '_')
                {
                    sb.Append(c);
                }
            }
            return sb.ToString();
        }
}