Dropdownlist avoid postback in c#

Question

User-2004582644 posted

Hi,

I have a `dropdownlist control` (ddl) on gridview.

There are these values in the ddl control "A" and "B" and "C".

I need to avoid postback of the page when selected value in `dropdownlist control` (ddl) is changed.

And this working.

But this code not working correctly, because it's no longer possible to edit the gridview line.

The `CommandName="Edit"` in gridview has stopped working after inserted of `UpdatePanel`.

Can you help me?

   <asp:UpdatePanel ID="UpdatePanel1" runat="server">
        <Triggers>
            <asp:AsyncPostBackTrigger ControlID="gvProducts" 
                 EventName="SelectedIndexChanged" />
        </Triggers>
        <ContentTemplate>
            <asp:GridView ID="gvProducts" AutoGenerateColumns="False" 
                EmptyDataText="no data" EnableViewState="true"
                runat="server" 
                DataKeyNames="ID" 
               HorizontalAlign="Center">
                <AlternatingRowStyle CssClass="altrows" />
                <Columns>
                    <asp:TemplateField HeaderText="EDIT" ItemStyle-HorizontalAlign="Center">
                        <ItemTemplate>
                            <asp:ImageButton ID="imgbtnEdit" 
                                CommandName="Edit" runat="server"
                                ImageUrl="/Images/Edit.gif"
                                OnClientClick="return confirm('Confirm ?');" />
                        </ItemTemplate>
                    </asp:TemplateField>
                    <asp:TemplateField HeaderText="List" ItemStyle-HorizontalAlign="Center">
                        <ItemTemplate>
                            <asp:DropDownList runat="server"
                                ID="ddl"
                                AutoPostBack="true"
                                OnSelectedIndexChanged="ddl_SelectedIndexChanged">
                                <asp:ListItem Text="A" Value="A" />
                                <asp:ListItem Text="B" Value="B" />
                                <asp:ListItem Text="C" Value="C" />
                            </asp:DropDownList>
                        </ItemTemplate>
                    </asp:TemplateField>
            </asp:GridView>
        </ContentTemplate>
    </asp:UpdatePanel>

    protected void gvProducts_RowEditing(object sender, GridViewEditEventArgs e)
    {
        string sID = gvProducts.DataKeys[e.NewEditIndex].Value.ToString();

        string queryString = "sDetails.aspx?sID=" + sID.ToString().ToUpper();
        string newWin = "var Mleft = (screen.width/2)-(1200/2);var Mtop = (screen.height/2)-(700/2);window.open('" + queryString + "','_blank','height=700,width=1200,status=yes,toolbar=no,scrollbars=yes,menubar=no,location=no,top=\'+Mtop+\', left=\'+Mleft+\';');";
        ClientScript.RegisterStartupScript(this.GetType(), "pop", newWin, true);
    }

    protected void ddl_SelectedIndexChanged(object sender, EventArgs e)
    {
        GridViewRow gvr = (GridViewRow)(((Control)sender).NamingContainer);
        string sIDdataKey = this.gvProducts.DataKeys[gvr.RowIndex].Value.ToString();
        DropDownList duty = (DropDownList)gvr.FindControl("ddl");

        sql = String.Format(@" UPDATE `tbl` ");
        sql += String.Format(" SET `Letter`= ? ");
        sql += String.Format(" WHERE ID= ?; ");

        using (OdbcConnection cn =
                new OdbcConnection(ConfigurationManager.ConnectionStrings["cn"].ConnectionString))
        {
            using (OdbcCommand command =
                    new OdbcCommand(sql, cn))
            {
                try
                {
                    command.Connection.Open();
                    command.Parameters.AddWithValue("param1", duty.SelectedItem.Value.ToString());
                    command.Parameters.AddWithValue("param2", sIDdataKey.ToString());
                    command.ExecuteNonQuery();
                    BindData();
                }
                catch (Exception ex)
                {
                    throw ex;
                }
                finally
                {
                    command.Connection.Close();
                }
            }
        }
    }

Answer 1

User-1330468790 posted

Hi Mark Sunderland,

  

But this code not working correctly, because it's no longer possible to edit the gridview line.

The `CommandName="Edit"` in gridview has stopped working after inserted of `UpdatePanel`.

This problem is located in the code behind where you register startup script using below code

protected void gvProducts_RowEditing(object sender, GridViewEditEventArgs e)
    {
        string sID = gvProducts.DataKeys[e.NewEditIndex].Value.ToString();

        string queryString = "sDetails.aspx?sID=" + sID.ToString().ToUpper();
        string newWin = "var Mleft = (screen.width/2)-(1200/2);var Mtop = (screen.height/2)-(700/2);window.open('" + queryString + "','_blank','height=700,width=1200,status=yes,toolbar=no,scrollbars=yes,menubar=no,location=no,top=\'+Mtop+\', left=\'+Mleft+\';');";
        ClientScript.RegisterStartupScript(this.GetType(), "pop", newWin, true);
    }

However, since you put the controls into the UpdatePanel control, the client-script-related part should be changed correspondingly.

You should no longer use "ClientScript" to register scripts. Instead, you should use "ScriptManager".

  

Solution:

Change the code as below

protected void gvProducts_RowEditing(object sender, GridViewEditEventArgs e)
        {
            string sID = gvProducts.DataKeys[e.NewEditIndex].Value.ToString();

            string queryString = "sDetails.aspx?sID=" + sID.ToString().ToUpper();
            string newWin = "var Mleft = (screen.width/2)-(1200/2);var Mtop = (screen.height/2)-(700/2);window.open('" + queryString + "','_blank','height=700,width=1200,status=yes,toolbar=no,scrollbars=yes,menubar=no,location=no,top=\'+Mtop+\', left=\'+Mleft+\';');";
            ScriptManager.RegisterStartupScript(this,this.GetType(), "pop", newWin, true);
        }

  

You may want to read the official document about Script registering for UpdatePanel. 

Click this link to read more about

• When you should use RegisterStartupScript method of ScriptManager
• and when you should use RegisterStartupScript method of the ClientScriptManager class

PS: In the "Remarks" section under the "RegisterStartupScript(Page, Type, String, String, Boolean)"  subtitle

  

Hope this can help you.

Best regards,

Sean

Answer 2

User-2004582644 posted

Hello Sean, thank you for reply.

I have tried your suggestion without success because the `CommandName="Edit"` in gridview not open page for edit row of gridview

Can you help me ?

Answer 3

User314352500 posted

Hope this can help you.

<asp:GridView ID="GridView1" AutoGenerateColumns="False"
    EmptyDataText="no data" EnableViewState="true"
    runat="server"
    DataKeyNames="ID"
    HorizontalAlign="Center">
    <AlternatingRowStyle CssClass="altrows" />
    <Columns>
        <asp:TemplateField HeaderText="EDIT" ItemStyle-HorizontalAlign="Center">
            <ItemTemplate>
                <asp:ImageButton ID="imgbtnEdit"
                    CommandName="Edit" runat="server"
                    ImageUrl="/Images/Edit.gif"
                    OnClientClick="return confirm('Confirm ?');" />
            </ItemTemplate>
        </asp:TemplateField>

        <asp:TemplateField HeaderText="List" ItemStyle-HorizontalAlign="Center">
            <ItemTemplate>
                <asp:UpdatePanel ID="UpdatePanel1" runat="server">
                    <Triggers>
                        <asp:AsyncPostBackTrigger ControlID="gvProducts"
                            EventName="SelectedIndexChanged" />
                    </Triggers>
                    <ContentTemplate>
                        <asp:DropDownList runat="server"
                            ID="ddl"
                            AutoPostBack="true"
                            OnSelectedIndexChanged="ddl_SelectedIndexChanged">
                            <asp:ListItem Text="A" Value="A" />
                            <asp:ListItem Text="B" Value="B" />
                            <asp:ListItem Text="C" Value="C" />
                        </asp:DropDownList>
                    </ContentTemplate>
                </asp:UpdatePanel>
            </ItemTemplate>
        </asp:TemplateField>