Changing DropDown Selected Item Based on Selected Value (ASP.NET)

Question

I have a dropdown list on my page (ddlProgram) which is populated via a database query like so:

Using dbContext as IRFEntities = New IRFEntities
    Dim getPrograms = (From p in dbContext.IRF_Program _
                       Order By p.name _
                       Select p)
    ddlProgram.DataSource = getPrograms
    ddlProgram.DataTextField = "name"
    ddlProgram.DataValueField = "id"
    ddl.Program.DataBind()
End Using

So, for example, one might have a DataTextField of "Education" and an ID of "221".

Now, I prepopulate the form with information about the individual visiting the site (if available) - including the dropdown list like so:

If getProspect IsNot Nothing Then
  If getProspect.user_id Is Nothing Then
    ddlProgram.SelectedValue = getProspect.Program
  End If
End If

The Program property contains a number that matches the ID of a Program. So, for example, this individual might have a Program of "221" which would match the "221" of Education mentioned above.

Currently the application successfully sets the SelectedValue to "221" for the DropDownList (ddlProgram), but the SelectedItem of the DDL remains the same (e.g., if it is initially "History" with an ID of "1" after the prepopulation it is "History" with an ID of "221").

What I'm trying to make happen is that the SelectedItem is updated to item which corresponds with the SelectedValue. So, in the end, if the individual has "221" for "Education" selected when the form is prepopulated they would see Education as the selected item and the selected value would be set correctly, whereas right now the form is showing the wrong SelectedItem but has the right SelectedValue behind the scenes.

Here is a more complete idea of the code flow from the Page_Load event:

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If Page.IsPostBack = False Then
        ' If prospect is coming from unique url
        Dim prospect_url As String = Page.RouteData.Values("value")
        ' Save prospect_url into session variable
        Session("prospect_url") = prospect_url
        Using dbContext As IRFEntities = New IRFEntities
            ' Prepopulate the programs dropdown.
            Dim getPrograms = (From p In dbContext.IRF_Program _
                            Order By p.name _
                             Select p)
            ddlProgram.DataSource = getPrograms
            ddlProgram.DataTextField = "name"
            ddlProgram.DataValueField = "id"
            ddlProgram.DataBind()
        End Using
        Using dbContext As IRFEntities = New IRFEntities
            ' Prepopulate the states dropdown.
            Dim getStates = (From p In dbContext.IRF_States _
                             Order By p.name _
                            Select p)
            ddlState.DataSource = getStates
            ddlState.DataTextField = "name"
            ddlState.DataValueField = "id"
            ddlState.DataBind()
        End Using
        Using dbContext As IRFEntities = New IRFEntities
            ' Grab info. about prospect based on unique url.
            Dim getProspect = (From p In dbContext.IRF_Prospects _
                              Where p.url = prospect_url _
                              Select p).FirstOrDefault
            ' If they have a record...
            If getProspect IsNot Nothing Then
                If getProspect.user_id Is Nothing Then
                    ' Prepopulate the form with their information.
                    ' These must have a value, so we need to make sure that no column is null in the database.
                    ddlProgram.SelectedValue = getProspect.program
                    txtFirst.Text = getProspect.first_name
                    txtLast.Text = getProspect.last_name
                    txtAddress.Text = getProspect.address
                    txtCity.Text = getProspect.city
                    ddlState.SelectedValue = getProspect.state
                    txtZip.Text = getProspect.zip
                    txtPhone.Text = getProspect.phone
                    txtEmail.Text = getProspect.email_address
                    txtYearEnrolling.Text = getProspect.enrolling_in
                Else
                    ' Redirect them to login.
                    Response.Redirect("login.aspx")
                End If
            End If
        End Using
    End If
End Sub

The binding to the dropdownlist for the list of programs occurs only if the page is not a postback, the pulling in of the individual info. (including their selected program) occurs with each postback. however, the page is generally static, there shouldn't really be multiple postbacks (unless someone for whatever reason decides to refresh the page). — Dave Mackey
– Dave Mackey, Commented Oct 24, 2012 at 15:40
How do you know there is a difference between the selected value and item? — Amiram Korach
– Amiram Korach, Commented Oct 24, 2012 at 15:50
I knew it b/c I would then submit the values to the database and while the selecteditem didn't appear correct on the form page it posted the correct value to the database from selectedvalue. It seems to be working now. — Dave Mackey
– Dave Mackey, Commented Oct 24, 2012 at 15:53

Tanner · Accepted Answer · 2012-10-24 16:25:55Z

2

What you're doing looks like it should work. If you put a breakpoint after the setting of the value and check the SelectedItem text and value, do they appear as expected or mismatched?

Use the Immediate Window to check:

ddlProgram.SelectedItem.Text
ddlProgram.SelectedItem.Value

If they appear the same then I would presume the binding code is being refired and the list is being regenerated with the first item being selected.

To check this put a break point on the binding code and see if it is fired more than once and correct the order of the methods appropriately.

ADDED: If it works on your local environment it should work when published, if the code is the same? Looking at your code, I'd start by seperating out some of the databinding code into seperate methods rather than have everything in Page_Load, one becuase it's good practice and two because it will make debugging easier. Further than that I'm not sure what else to suggest.

edited Oct 24, 2012 at 16:25

answered Oct 24, 2012 at 15:48

Tanner

22.8k9 gold badges70 silver badges89 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Dave Mackey Over a year ago

Well, this is very strange...it just started working! But your suggestion was very helpful, thanks.

Dave Mackey Over a year ago

Okay, let me take that back. It works correctly on the localhost but when published to the production server it doesn't work correctly - it has the error mentioned in the original question.

Collectives™ on Stack Overflow

Changing DropDown Selected Item Based on Selected Value (ASP.NET)

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related