CODEWITHSUNDEEP
c#asp.netdrop-down-menupostback
Flo
Flo

Reputation: 986

dynamically filled DropDownList does not retain value on postback

I have a form which is made to "Create a new profile". My problem is about DropDownLists.

The first DropDown dynamically populate the second one in function of its value.

see this picture:

http://image.noelshack.com/fichiers/2013/22/1369819471-picture-help.png

And the following picture:

http://image.noelshack.com/fichiers/2013/22/1369830738-help2.png

You can see that my 2nd ddl ("Fonction") is correctly filled BUT when I click on the submit button, the value becomes the null value ("Sélectionnez...") and so my RequiredFieldValidator makes the page not valid!

It seems like my 2nd DropDownList is bounded on every postback even if it's not because of SelectedIndexChanged of my 1st DropDownList. The SelectedIndexChanged of the 1st DropDownList is always called on postback and so it throws "populateDdl()" at every PostBack (if a value is selected).

When I click on submit button, it registers a blank value in my database.

What am I missing?

Aspx code:

<asp:DropDownList ID="ddlTypePN" runat="server" DataSourceID="SqlTypePN" EnableViewState="true" 
        DataTextField="libelle" DataValueField="valeur" AutoPostBack="true" OnSelectedIndexChanged="ddlTypePN_SelectedIndexChanged" 
        OnDataBound="ddlTypePN_DataBound" > </asp:DropDownList> 

<asp:DropDownList runat="server" ID="ddlFctPN" AppendDataBoundItems="false" OnDataBound="ddlFctPN_DataBound" > </asp:DropDownList>

Code behind:

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        ddlTypeProf.DataBind(); // don't care
        ddlSsoSrc.DataBind(); // don't care
        ddlTypePN.DataBind(); // The ddl that populate my 2nd ddl
    }
}

protected void ddlTypePN_SelectedIndexChanged(object sender, EventArgs e)
{
    string type = ddlTypePN.SelectedValue.ToString().Trim();
    // if PNT
    if (type.ToUpper().Trim().Equals("PNT"))
    {               
        ddlFctPN.Enabled = true;
        ddlTypeAv.Enabled = true;
        rfvTypeAv.Enabled = true;
        populateDdl();

    }
    else if (type.ToUpper().Trim().Equals("PNC"))
    {                
        ddlFctPN.Enabled = true;
        ddlTypeAv.Enabled = false;
        rfvTypeAv.Enabled = false;
        populateDdl();
    }     
}

void populateDdl()
{
    string val = "fct"+ddlTypePN.SelectedValue.ToString().Trim(); // Used for SELECT
    SqlConnection sqlConn = new SqlConnection(ConfigurationManager.ConnectionStrings["My_DB"].ConnectionString);
    ddlFctPN.Items.Clear();
    DataTable subjects = new DataTable();
    try
    {
        SqlDataAdapter adapter = new SqlDataAdapter("My SELECT", sqlConn);
        adapter.Fill(subjects);

        ddlFctPN.DataSource = subjects;
        ddlFctPN.DataTextField = "libelle";
        ddlFctPN.DataValueField = "valeur";
        ddlFctPN.DataBind();
    }
    catch (Exception ex)
    {
        lblErr.Text = ex.Message;
    }
    ddlFctPN.Items.Insert(0, new ListItem("Sélectionnez...", "null"));
}

Upvotes: 4

Views: 34233

Answers (9)

Loony_D
Loony_D

Reputation: 41

In my case this issue occurred because the DataValueField values assigned to drop down were empty. dropdownName.DataValueField must be unique for all entries.

Upvotes: 0

TylerH
TylerH

Reputation: 21100

Solution moved to an answer from the question:

I finally found what the problem was. Every control was in an <asp:Table>, and I had to set EnableViewState="true" on this table in order to be able to keep the value after postback.

Upvotes: 1

fernando yevenes
fernando yevenes

Reputation: 152

ok solucion 

<script type="text/javascript">
    function MtCambioRegion() {
        // con JQUERY



        //var regionId = $('#<%= ddlregion.ClientID %>').val();
        // sin JQUERY
        var regionId = document.getElementById('ContentBody_ddlRegion').value;
       //  var regionId = document.getElementById('ContentBody_CtrContenedoAjax_ddlRegion').value
       // alert('metodo region : ' + regionId );
        GetCitiesOfRegion(regionId);
    }

    function GetCitiesOfRegion(regionId) {
        // alert('Funcion ' + regionId );
        var actionData = "{'regionId': '" + regionId + "'}";
        $.ajax({
            type: "POST",
            url: "WebTespRegionComuna.aspx/GetProComunas",
            data: actionData,
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            success: function (r) {
                var ddlComuna = $("[id*=ddlComuna]");
                ddlComuna.empty().append('');

                $.each(r.d, function () {
                    ddlComuna.append($("<option></option>").val(this['id']).html(this['nombre']));
                });
            }
        });

    }

    function FnSelComuna() {
        var x = document.getElementById("ContentBody_ddlComuna").value;
        // alert(x);
        document.getElementById('ContentBody_txtComunaHiden').value = x;
    }

// formulario aspx

Public Class WebTespRegionComuna
Inherits System.Web.UI.Page

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If Not Page.IsPostBack Then
        'ControlSystema.GetSearhRegionList(ddlRegion)

        Dim _ControlSystema As New ControlSystema
        With _ControlSystema
            .MtRegionList(ddlRegion)
        End With
        _ControlSystema = Nothing


    End If

End Sub


<System.Web.Services.WebMethod()> _
Public Shared Function GetProComunas(regionId As String) As List(Of ComunaList)
    Dim _ControlSystema As New ControlSystema
    Dim _lista As List(Of ComunaList)
    With _ControlSystema
        _lista = .GetSearchComunaList(regionId)
    End With
    _ControlSystema = Nothing
    Return _lista
End Function

Private Sub btnGuardarDatos_Click(sender As Object, e As System.EventArgs) Handles btnGuardarDatos.Click
    Try
        Dim valorcomuna As String = ddlComuna.SelectedValue
        valorcomuna = txtComunaHiden.Text


        Dim valorregion As String = ddlRegion.SelectedValue.ToString()
        Dim _valor As String = "punto de quiebre"

    Catch ex As Exception

    End Try
End Sub End Class

Upvotes: -1

Charlie
Charlie

Reputation: 1

After many hours of trying to figure out a similar problem and why my dropdown wouldn't change, I checked my data and while the DataTextField info was different, the DataTextValues were the same and it was just pulling the first one each time. Check your data and see if they have different values.

Upvotes: -1

user2024891
user2024891

Reputation:

From your mark up you haven't set the AutoPostBack property on the second drop down. So it shouldn't fire a post back when the second drop down index has changed (unless you are programmatically causing a post back).

I've copied your code into my solution, it seems to be behaving...

<asp:Label ID="lblErr" runat="server"></asp:Label>
<asp:DropDownList ID="ddlTypePN" runat="server" EnableViewState="true"
    AutoPostBack="true" OnSelectedIndexChanged="ddlTypePN_SelectedIndexChanged"
    OnDataBound="ddlTypePN_DataBound">
</asp:DropDownList>

<asp:DropDownList runat="server" ID="ddlFctPN" AppendDataBoundItems="false" OnDataBound="ddlFctPN_DataBound">
</asp:DropDownList>

And the code...

protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                ListItemCollection items = new ListItemCollection();
                items.Add(new ListItem("PNT", "PNT"));
                items.Add(new ListItem("PNC", "PNC"));

                ddlTypePN.DataSource = items;
                ddlFctPN.DataBind();
                ddlTypePN.DataBind(); // The ddl that populate my 2nd ddl

                ddlTypePN.Items.Insert(0, new ListItem("Sélectionnez...", "null"));
            }
        }

        protected void ddlTypePN_SelectedIndexChanged(object sender, EventArgs e)
        {
            string type = ddlTypePN.SelectedValue.ToString().Trim();

            // if PNT
            if (type.ToUpper().Trim().Equals("PNT"))
            {
                ddlFctPN.Enabled = true;
                populateDdl();

            }
            else if (type.ToUpper().Trim().Equals("PNC"))
            {
                ddlFctPN.Enabled = true;
                populateDdl();
            }        
        }

        protected void ddlTypePN_DataBound(object sender, EventArgs e)
        {

        }

        protected void ddlFctPN_DataBound(object sender, EventArgs e)
        {

        }

        void populateDdl()
        {

            ddlFctPN.Items.Clear();
            lblErr.Visible = false;

            try
            {
                ListItemCollection items = new ListItemCollection();
                items.Add(new ListItem("One", "1"));
                items.Add(new ListItem("Two", "2"));
                items.Add(new ListItem("Three", "3"));

                ddlFctPN.DataSource = items;
                ddlFctPN.DataBind();
            }
            catch (Exception ex)
            {
                lblErr.Text = ex.Message;
                lblErr.Visible = true;
            }


            ddlFctPN.Items.Insert(0, new ListItem("Sélectionnez...", "null"));

        }

    }

Upvotes: 1

vishal mane
vishal mane

Reputation: 296

you are population DD1 in every post back

to avoid this use 

if(!IsPostBack)    
 {
   populateDdl();
 }

Upvotes: 1

Roar
Roar

Reputation: 2167

U can use CascadingDropDown like: 

<ajaxToolkit:CascadingDropDown ID="CDD1" runat="server"
    TargetControlID="DropDownList2"
    Category="Model"
    PromptText="Please select a model"
    LoadingText="[Loading models...]"
    ServicePath="CarsService.asmx"
    ServiceMethod="GetDropDownContents"
    ParentControlID="DropDownList1"
    SelectedValue="SomeValue" />

Upvotes: 0

Ayyappan Sekaran
Ayyappan Sekaran

Reputation: 1036

if(!IsPostBack)

 {

  populateDdl();

 }

Upvotes: 2

Mahmoude Elghandour
Mahmoude Elghandour

Reputation: 2931

put this code under this condition 

if(!Page.IsPostBack)
            {

       // Your Code Here

            }

Upvotes: 1

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