Web Service in C# with JSON return format

You can very easily write web service with JSON data return format.

please check below method, this may help you.

[WebMethod(Description = "Gets Student information")]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public string GetStudent()
    {
        SqlConnection objConnection = new SqlConnection(strconnectionString);
        SqlCommand objCommand = new SqlCommand("SELECT * FROM Student", objConnection);
        DataSet objDataSet = new DataSet();
        SqlDataAdapter objDataAdapter = new SqlDataAdapter(objCommand);
        objDataAdapter.Fill(objDataSet, "reading");
        objConnection.Close();
        // Create a multidimensional jagged array
        string[][] JaggedArray = new string[objDataSet.Tables[0].Rows.Count][];
        int i = 0;
        foreach (DataRow rs in objDataSet.Tables[0].Rows)
        {
            JaggedArray[i] = new string[] { rs["Name"].ToString(), rs["Roll"].ToString(), rs["Class"].ToString() };
            i = i + 1;
        }
        // Return JSON data

        JavaScriptSerializer js = new JavaScriptSerializer();
        string strJSON = js.Serialize(JaggedArray);
        return strJSON;

    }