/// <summary>
/// 对字符串进行sql格式化，并且符合like查询的格式。
/// </summary>
/// <param name="str">要转换的字符串</param>
/// <returns>格式化后的字符串</returns>
public static string ToLikeSql(string sqlstr)
{
if (sqlstr == null) return "";
StringBuilder str = new StringBuilder(sqlstr);
str.Replace("'","''");
str.Replace("[","[[]");
str.Replace("%","[%]");
str.Replace("_","[_]");
return str.ToString();
}