C# Use RichTextBox to implement the function of replacing text and changing font color

private void GenerateEntity()
{
  try
  {
    string result = ChangeWords("specific content...");
     = result;
    ChangeColor();
  }
  catch (Exception ex)
  {
    ("Class generation failed! Error message:" + );
  }
}
private string ChangeWords(string content)
{
  //Replace "nvarchar", "varchar", "nchar", and then replace "char"  //Otherwise "nvarchar", "varchar", and "nchar" will be replaced with  //nvarstring", "varstring", and "nstring" cannot be replaced by the original rules  string result = (content, "nvarchar", "string");
  // When performing the next step of replacement, be sure to return the result of the above step of replacement as the data source instead of the content  //Because the content value has not changed  result = (result, "varchar", "string");
  result = (result, "nchar", "string");
  result = (result, "char", "string");
  result = (result, "tinyint", "int");
  result = (result, "smallint", "int");
  result = (result, "bigint", "int");
  result = (result, "datetime", "DateTime");
  return result;
}

private void ChangeColor()
{
   = 0;
   = ;
   = ;
  // When the column comment is not empty, change the color of the column comment  if ( > 0)
  {
    ChangeKeyColor(listDescription, );
  }
  ChangeKeyColor("namespace", );
  ChangeKeyColor("public", );
  ChangeKeyColor("class", );
  ChangeKeyColor("/// <summary>",);
  ChangeKeyColor("///", );
  ChangeKeyColor("/// </summary>", );
  ChangeKeyColor("int", );
  ChangeKeyColor("double", );
  ChangeKeyColor("float", );
  ChangeKeyColor("char", );
  ChangeKeyColor("string", );
  ChangeKeyColor("bool", );
  ChangeKeyColor("decimal", );
  ChangeKeyColor("enum", );
  ChangeKeyColor("const", );
  ChangeKeyColor("struct", );
  ChangeKeyColor("DateTime", );
  ChangeKeyColor("get",);
  ChangeKeyColor("set", );
}
public void ChangeKeyColor(string key, Color color)
{
  Regex regex = new Regex(key);
  //Find out all the keywords to replace in the content  MatchCollection collection = ();
  //Replace colors one by one for all keywords to replace colors  foreach (Match match in collection)
  {
    //The start position, length and color are indispensable     = ;
     = ;
     = color;
  }
}
public void ChangeKeyColor(List<string> list, Color color)
{
  foreach (string str in list)
  {
    ChangeKeyColor(str, color);
  }
}