check duplicate data with javascript

Question

i am writing web application in asp.net . i have a input form . i want when the client click on save Button before insert, check this data is in data base or not . i have written it with code behind . but i want do this with java script because when i i use code behind the page refresh . this is my .net code for check duplicate data:

SqlCommand commandrepeat1 = new SqlCommand("Select code from CmDet where code = " + txtcode.Text + " and company = " + DataBase.globalcompany.ToString() + " order by code desc");
            commandrepeat1.Connection = objconnection;
            objconnection.Close();
            objconnection.Open();
            SqlDataReader drmax1;
            drmax1 = commandrepeat1.ExecuteReader();
            drmax1.Read();
            if (drmax1.HasRows)
            {
                MessageBox.Show("Duplicate data . try again!!! ");
                txtcode.Focus();
                objconnection.Close();
                return;
            }
            objconnection.Close();
        }
        catch
        {
            objconnection.Close();
        }

Answer 1

You should have your ASP.NET button implement both the OnClick event (to execute server-side code once it is determined that there is not duplicate data) and OnClientClick event (to execute your JavaScript that will call to check if there is duplicate data).

I suggest the following:

In JavaScript, add a jQuery click event to your button, like this:

$( "#myButton" ).click(function() {

});

Note: I have assumed the name of your button to be myButton, change it to match the ID of your button in markup.

Now you will need to call server-side to execute your logic to look for duplicate data. I recommend using ASP.NET AJAX Page Methods invoked via the jQuery .ajax() function, like this:

$.ajax({
    type: "POST",
    url: "YourPage.aspx/DoesDataExist",
    data: "{'codeValue': $('#myTextBox').val()}",
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: function(msg) {
        if(msg.d) {
            // This is a duplicate, alert user with message
            // Block the server-side click from happening with return false;
            return false;
        }
    }
});

Finally, we need to build the server-side code that will handle the page method called by the jQuery above, like this:

[WebMethod]
public static bool DoesDataExist()
{
    SqlCommand commandrepeat1 = new SqlCommand("Select code from CmDet where code = " + txtcode.Text + " and company = " + DataBase.globalcompany.ToString() + " order by code desc");
    commandrepeat1.Connection = objconnection;
    objconnection.Close();
    objconnection.Open();
    SqlDataReader drmax1;
    drmax1 = commandrepeat1.ExecuteReader();
    drmax1.Read();
    if (drmax1.HasRows)
    {
        objconnection.Close();
        return true;
    }
    objconnection.Close();

    return false;
}