How to pass a textbox value to web method which is located in asmx file using ajax?

Hi,

I have a got a web page that has a javascript file with ajax call to a web method. The web method contains a call to database using stored procedure with parameter. If the sent parameter matches, the data will be returned in a array format. My question is how do I pass the textbox value to this ajax call and get the cmd.Parameters.Add in the execution of the stored procedure to retrieve the result. 

These is my code : - I am actually passing the date in the textbox txtDate as the parameter.

1. ASPX page : -

   <div><b>Date:</b> <asp:TextBox ID="txtDate" runat="server" ClientIDMode="Static"/><asp:Button ID="Button1" runat="server" Text="OK" OnClick="Button1_Click"/></div>

   JS file

2. $.ajax({
       alert: ("It has started"),
   
       type: "post",
       url: "BarChart.asmx/CreateSubListTable",
       // data: "{ firstName: 'Aidy', lastName: 'F' }",
       contentType: "application/json; charset=utf-8",
       dataType: "json",
       success: function (res, textStatus) {
           var data1 = JSON.parse(res.d);
           console.log(data1);
           createbarchart(data1);
           //pass the array of data1 into a function
           //drawdoughnutchat(data1);
           // console.log("Function called");
       },
       error: function (xhr, textStatus, error) {
           console.log(xhr.responseText);
           console.log(xhr.statusText);
           console.log(textStatus);
           console.log(error);
       }
   })

   3. SQL stored procedure in BarChart.asmx

3.  public List<DenDate> AddListintoParentArr()
           {
               List<DenDate> resultslistden = new List<DenonDate>();
               using (SqlConnection con = new SqlConnection(constr))
               {
                   using (SqlCommand cmd = new SqlCommand())
                   {
                       cmd.Connection = con;
                       cmd.CommandType = CommandType.StoredProcedure;
                       cmd.CommandText = "CheckforDateinTablesRough";
                       //cmd.Parameters.Add("@Value", SqlDbType.Date).Value = DateTime.ParseExact(LabelDate.Text, "dd/MM/yyyy", null);
                       con.Open();
   
                       SqlDataReader rdr = cmd.ExecuteReader();
                       while (rdr.Read())
                       {
                           DenDate results = new DenDate
                           {
                               RunningJobTblName = rdr["TableName"].ToString(),
                               TblNameShort = rdr["ShortForm"].ToString(),
                               JobOrderName = rdr["JobOrderName"].ToString(),
                               DeeProfileID = Convert.ToInt32(rdr["DeeProfileID"])
                           };
                           resultslistden.Add(results);
                       }
                   }
               }
   
   
   
   
               return resultslistden;
               //return jsonlist;
               //return resultslistden.ToJSON2();
           }

   Please assist. Thank you in advance. Any guidance would be helpful.