C Implementation Method Set for Filtering sql Special Characters

This article illustrates a collection of methods for C # to filter sql special characters. Share it for your reference, as follows:

1.

/// <summary>
///  Filter unsafe strings 
/// </summary>
/// <param name="Str"></param>
/// <returns></returns>
public static string FilteSQLStr(string Str)
{
  Str = Str.Replace("'", "");
  Str = Str.Replace("\"", "");
  Str = Str.Replace("&", "&amp");
  Str = Str.Replace("<", "&lt");
  Str = Str.Replace(">", "&gt");
  Str = Str.Replace("delete", "");
  Str = Str.Replace("update", "");
  Str = Str.Replace("insert", "");
  return Str; 
}

2.

#region  Filter  Sql  Injection script in statement string 
/// <summary>
///  Filter  Sql  Injection script in statement string 
/// </summary>
/// <param name="source"> String passed in </param>
/// <returns> Filtered string </returns>
public static string SqlFilter(string source)
{
 // Replace single quotation marks with two single quotation marks 
 source = source.Replace("'", "''");
 // Half-angle title is replaced by full-angle title to prevent multiple statements from being executed 
 source = source.Replace(";", " ; ");
 // Replace half-angle brackets with full-angle brackets 
 source = source.Replace("(", " ( ");
 source = source.Replace(")", " ) ");
 /////////////// To replace with regular expressions, prevent letters from being capitalized ////////////////////
 // Remove command keywords for executing stored procedures 
 source = source.Replace("Exec", "");
 source = source.Replace("Execute", "");
 // Remove system stored procedure or extended stored procedure keywords 
 source = source.Replace("xp_", "x p_");
 source = source.Replace("sp_", "s p_");
 // Prevent 16 Binary injection 
 source = source.Replace("0x", "0 x");
 return source;
}
#endregion

3.

///  Filter SQL Characters. 
/// </summary>
/// <param name="str"> To filter SQL A string of characters. </param>
/// <returns> Filtered out SQL A string of characters. </returns>
public static string ReplaceSQLChar(string str)
{
 if (str == String.Empty)
  return String.Empty; str = str.Replace("'", " ' ");
 str = str.Replace(";", " ; ");
 str = str.Replace(",", ",");
 str = str.Replace("?", "?");
 str = str.Replace("<", " < ");
 str = str.Replace(">", " > ");
 str = str.Replace("(", "(");
 str = str.Replace(")", ")");
 str = str.Replace("@", " @ ");
 str = str.Replace("=", " = ");
 str = str.Replace("+", " + ");
 str = str.Replace("*", " * ");
 str = str.Replace("&", " & ");
 str = str.Replace("#", " # ");
 str = str.Replace("%", " % ");
 str = str.Replace("$", " $ ");
 return str;
}

4.

/// <summary>
///  Filter mark 
/// </summary>
/// <param name="NoHTML"> Include HTML Scripts, database keywords, special character source code  </param>
/// <returns> Text that has been stripped of marks </returns>
public string NoHtml(string Htmlstring)
{
 if (Htmlstring == null)
 {
  return "";
 }
 else
 {
  // Delete script 
   Htmlstring = Regex.Replace(Htmlstring, @"<script[^>]*?>.*?</script>", "", RegexOptions.IgnoreCase);
  // Delete HTML
  Htmlstring = Regex.Replace(Htmlstring, @"<(.[^>]*)>", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, @"([\r\n])[\s]+", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, @"-->", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, @"<!--.*", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, @"&(quot|#34);", "\"", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, @"&(amp|#38);", "&", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, @"&(lt|#60);", "<", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, @"&(gt|#62);", ">", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, @"&(nbsp|#160);", " ", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, @"&(iexcl|#161);", "\xa1", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, @"&(cent|#162);", "\xa2", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, @"&(pound|#163);", "\xa3", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, @"&(copy|#169);", "\xa9", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, @"&#(\d+);", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "xp_cmdshell", "", RegexOptions.IgnoreCase);
  // Delete database-related words 
  Htmlstring = Regex.Replace(Htmlstring, "select", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "insert", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "delete from", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "count''", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "drop table", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "truncate", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "asc", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "mid", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "char", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "xp_cmdshell", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "exec master", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "net localgroup administrators", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "and", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "net user", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "or", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "net", "", RegexOptions.IgnoreCase);
  //Htmlstring = Regex.Replace(Htmlstring, "*", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "-", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "delete", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "drop", "", RegexOptions.IgnoreCase);
  Htmlstring = Regex.Replace(Htmlstring, "script", "", RegexOptions.IgnoreCase);
  // Special character 
   Htmlstring = Htmlstring.Replace("<", "");
  Htmlstring = Htmlstring.Replace(">", "");
  Htmlstring = Htmlstring.Replace("*", "");
  Htmlstring = Htmlstring.Replace("-", "");
  Htmlstring = Htmlstring.Replace("?", "");
  Htmlstring = Htmlstring.Replace("'", "''");
  Htmlstring = Htmlstring.Replace(",", "");
  Htmlstring = Htmlstring.Replace("/", "");
  Htmlstring = Htmlstring.Replace(";", "");
  Htmlstring = Htmlstring.Replace("*/", "");
  Htmlstring = Htmlstring.Replace("\r\n", "");
  Htmlstring = HttpContext.Current.Server.HtmlEncode(Htmlstring).Trim();
  return Htmlstring;
 }
}

5.

public static bool CheckBadWord(string str)
{
string pattern = @"select|insert|delete|from|count\(|drop table|update|truncate|asc\(|mid\(|char\(|xp_cmdshell|exec master|netlocalgroup administrators|net user|or|and";
if (Regex.IsMatch(str, pattern, RegexOptions.IgnoreCase))
return true;
return false;
}
public static string Filter(string str)
{
string[] pattern ={ "select", "insert", "delete", "from", "count\\(", "drop table", "update", "truncate", "asc\\(", "mid\\(", "char\\(", "xp_cmdshell", "exec master", "netlocalgroup administrators", "net user", "or", "and" };
for (int i = 0; i < pattern.Length; i++)
{
str = str.Replace(pattern[i].ToString(), "");
}
return str;
}

I hope this article is helpful to everyone's C # programming.