String Replace method is not case sensitive

Replace found there is no way to distinguish Like compare the size of the contrast at the time of writing C # code, so I wrote a method ReplaceStr

as follows:

   private string ReplaceStr(string str, string key, string value,bool IgnoreCase)
        {
            string newstr = str.Replace(key, value);

            int i = newstr.IndexOf(key, StringComparison.OrdinalIgnoreCase);

            if (i > 0&&IgnoreCase)
            {
                key = newstr.Substring(i, key.Length);
                return ReplaceStr(newstr, key, value,IgnoreCase);
            }
            else
            {
                return newstr;
            }

        }

The main use of or 
newstr.IndexOf (string, StringComparison.OrdinalIgnoreCase) have StringComparison.OrdinalIgnoreCase property is not case sensitive.

Reproduced in: https: //www.cnblogs.com/springyangwc/archive/2011/01/31/1948425.html