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。

最短的路只有三条线……

public static string RemoveSpecialCharacters(string str)
{
    var sb = new StringBuilder();
    foreach (var c in str.Where(c => c >= '0' && c <= '9' || c >= 'A' && c <= 'Z' || c >= 'a' && c <= 'z' || c == '.' || c == '_')) sb.Append(c); 
    return sb.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。

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();
}

我建议创建一个简单的查找表，您可以在静态构造函数中初始化它，以将任何字符组合设置为有效。这让您可以进行快速、单一的检查。

edit

另外，为了提高速度，您需要将StringBuilder的容量初始化为输入字符串的长度。这将避免重新分配。这两种方法结合起来会给你速度和灵活性。

另一个编辑

我认为编译器可能会优化它，但作为风格和效率的问题，我建议foreach而不是for。

对于S&G, linq化的方式:

var original = "(*^%foo)(@)&^@#><>?:\":';=-+_";
var valid = new char[] { 
    'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 
    'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 'A', 'B', 'C', 'D', 
    'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 
    'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '1', '2', '3', '4', '5', '6', '7', '8', 
    '9', '0', '.', '_' };
var result = string.Join("",
    (from x in original.ToCharArray() 
     where valid.Contains(x) select x.ToString())
        .ToArray());

然而，我不认为这是最有效的方法。