//convert xml string to dataset, and WriteXmlSchema to string
System.IO.
DataSet dsResponse = new DataSet();StringReader sr = new System.IO.StringReader(responseMessage);//System.IO.StreamReader sr = new System.IO.StreamReader(
dsResponse.ReadXml(sr);
System.Text.
StringBuilder builder = new System.Text.StringBuilder();// Create the StringWriter object with the StringBuilder object.
System.IO.
StringWriter writer = new System.IO.StringWriter(builder);// Write the schema into the StringWriter.
dsResponse.WriteXmlSchema(writer);
//put schema in string
string xmlSchema = writer.ToString();