json convert to string

Question

this is my code 

 

private void btnKeywords_Click(object sender, EventArgs e)

{

string document = string.Empty;

if (chkDocument.Checked == true)

{

document = txtDocument1.Text.Trim() + " " + txtDocument2.Text.Trim();

} else

{

document = txtDocument1.Text.Trim();

}

string result = clas.keywords(document);

// var jsonString = Newtonsoft.Json.JsonConvert.SerializeObject(result);

dynamic response = JsonConvert.DeserializeObject(result);

List Kewordlist = response.keywords.ToObject >();

//List