DBNull on DropDownList Help

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Good Afternoon

I'm hoping someone can assist as I'm obviously missing something here.

Basically I have a drop down list of a category when viewing in the webpage and selecting a job with a category its coming up with an error

An exception of type 'System.ArgumentOutOfRangeException' occurred in System.Web.dll but was not handled in user code

My code is below and it refers to the line DDCat

VB

Protected Sub DDOFIREF_SelectedIndexChanged(sender As Object, e As EventArgs) Handles DDOFIREF.SelectedIndexChanged

      'LblRef.Text = DDOFIREF.Text

      Dim dv As New Data.DataView 'use the id of your SqlDataSource below'
      dv = AccessDataSource3.Select(DataSourceSelectArguments.Empty)
      LblUser.Text = dv.Table.Rows(0)("UserN")
      LblDept.Text = dv.Table.Rows(0)("Dept")
      lblroot.Text = dv.Table.Rows(0)("Root")
      lblassign.Text = dv.Table.Rows(0)("AssignTo")
      txtdetails.Text = dv.Table.Rows(0)("Details")
      txtctc.Text = dv.Table.Rows(0)("CostCompany")
      lblref2.Text = dv.Table.Rows(0)("ref")
      DDCat.Text = If(IsDBNull(dv.Table.Rows(0)("Category")), DDCat.SelectedItem.ToString = "Select one", dv.Table.Rows(0)("Category"))
      txtact.Text = If(IsDBNull(dv.Table.Rows(0)("Action")), String.Empty, dv.Table.Rows(0)("action"))
      txtofi.Text = If(IsDBNull(dv.Table.Rows(0)("OfiNotes")), String.Empty, dv.Table.Rows(0)("OfiNotes"))

Any help would be greatly appreciated.

Thanks

Posted 11-Jun-15 5:34am

Emm4

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Comments

Sergey Alexandrovich Kryukov 11-Jun-15 11:58am

Check if the number of rows in dv.Table is zero...
—SA

Emm4 11-Jun-15 12:23pm

Hi Sergey, I have checked and they are set at 0 .....

Sergey Alexandrovich Kryukov 11-Jun-15 12:31pm

What do you mean by that? If count is zero, indexing element at (0) will throw this exception.
After all, run it under the debugger.
—SA

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CHill60 · Answer 1 · 2015-06-11T09:31:00

Whenever you are getting data from a database you should always check that the query has returned something before attempting to use it. For example

VB

Protected Sub DDOFIREF_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) Handles DDOFIREF.SelectedIndexChanged

    'LblRef.Text = DDOFIREF.Text

    Dim dv As New Data.DataView 'use the id of your SqlDataSource below'
    dv = AccessDataSource3.Select(DataSourceSelectArguments.Empty)

    If dv.Table.Rows.Count > 0 Then
        LblUser.Text = dv.Table.Rows(0)("UserN")
        LblDept.Text = dv.Table.Rows(0)("Dept")
        lblroot.Text = dv.Table.Rows(0)("Root")
        lblassign.Text = dv.Table.Rows(0)("AssignTo")
        txtdetails.Text = dv.Table.Rows(0)("Details")
        txtctc.Text = dv.Table.Rows(0)("CostCompany")
        lblref2.Text = dv.Table.Rows(0)("ref")
        DDCat.Text = If(IsDBNull(dv.Table.Rows(0)("Category")), DDCat.SelectedItem.ToString = "Select one", dv.Table.Rows(0)("Category"))
        txtact.Text = If(IsDBNull(dv.Table.Rows(0)("Action")), String.Empty, dv.Table.Rows(0)("action"))
        txtofi.Text = If(IsDBNull(dv.Table.Rows(0)("OfiNotes")), String.Empty, dv.Table.Rows(0)("OfiNotes"))
    End If

End Sub

Simply put, if there are no rows returned then Rows(0) does not exist (nor Rows(1), Rows(2) etc) - and there is your exception being thrown.

It's worth checking how you have configured the AccessDataSource control - try running the query directly against the database to see what you get back.