[代碼收集]字符串去除特殊字符

if (String.IsNullOrEmpty(str))
    return str;
   
string okChars = "abcdefghijklmnopqrstuvwxyz1234567890 _-";
str = str.Trim().ToLowerInvariant();
   
var sb = new StringBuilder();
foreach (char c in str.ToCharArray())
{
    string c2 = c.ToString();
    if (okChars.Contains(c2))
        sb.Append(c2);
}
string str2 = sb.ToString();
str2= str2.Replace(" ", "_");
str2= str2.Replace("-", "_");
while (str2.Contains("__"))
    str2 = str2.Replace("__", "_");
return str2;