Hi,

I have a data grid view which includes a combo box column. The combo box column is the second column in the grid view. I have a button which fills the grid based on some conditions entered in a text box. The combo box is bound to a dataset and then the grid is bound to another dataset. This works fine the first time I click the button. However when I click the button the second time I get this error

Unable to cast object of type 'System.Windows.Forms.DataGridViewTextBoxColumn' to type 'System.Windows.Forms.DataGridViewComboBoxColumn'."

Could anyone let me know why this happens
The code behind the button is shown below

Private

Sub btnAssignGetPackage_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAssignGetPackage.Click

Try

Dim ds As DataSet = DB.GetPackagesUnionConfig(Me.cboEnviron.SelectedValue, Me.txtAssignFilter.Text)

Dim dsAreas As DataSet = DB.GetAreas(Me.cboEnviron.SelectedValue)

If ds.Tables(0).Rows.Count > 0 Then

Me.dgv_AssignSelectPackage.Visible = True

Me.btnAssignSavePackage.Visible = True

Dim lst As DataGridViewComboBoxColumn = CType(dgv_AssignSelectPackage.Columns(1), DataGridViewComboBoxColumn)

lst.DataSource = Nothing

lst.DataSource = dsAreas.Tables(0)

lst.DisplayMember = "AREA"

lst.ValueMember = "AREA"

Me.dgv_AssignSelectPackage.DataSource = Nothing

Me.dgv_AssignSelectPackage.DataSource = ds

Me.dgv_AssignSelectPackage.DataMember = ds.Tables(0).TableName

Else

Me.dgv_AssignSelectPackage.Visible = False

Me.btnAssignSavePackage.Visible = False

End If

Catch ex As Exception

MsgBox(ex.Message, MsgBoxStyle.Critical, "Error when retreiving Packages")

End Try

End Sub

Thanks in advance

Cooper

Hi,

Does the project throw the error at
Dim lst As DataGridViewComboBoxColumn = CType(dgv_AssignSelectPackage.Columns(1), DataGridViewComboBoxColumn) ?

Which way do you used to set the DataGridViewComboboxColumn? Setting DisplayIndex? If so, displayIndex is not the true index, it only changes the display column order. You can get the index by DataGridViewColumn.Index property. You'd better set a breakpoint at the CType method to check whether the columns(1) is typed of DataGridViewComboBoxColumn.

More information:

DataGridViewColumn.DisplayIndex Property

http://msdn.microsoft.com/en-us/library/system.windows.forms.datagridviewcolumn.displayindex.aspx

DataGridViewColumn Properties

http://msdn.microsoft.com/en-us/library/system.windows.forms.datagridviewcolumn_properties.aspx

If I misunderstood you, or you have further questions, please feel free to tell me.

Best regards,

Ling Wang

---

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Hi,

Does the project throw the error at
Dim lst As DataGridViewComboBoxColumn = CType(dgv_AssignSelectPackage.Columns(1), DataGridViewComboBoxColumn) ?

Which way do you used to set the DataGridViewComboboxColumn? Setting DisplayIndex? If so, displayIndex is not the true index, it only changes the display column order. You can get the index by DataGridViewColumn.Index property. You'd better set a breakpoint at the CType method to check whether the columns(1) is typed of DataGridViewComboBoxColumn.

More information:

DataGridViewColumn.DisplayIndex Property

http://msdn.microsoft.com/en-us/library/system.windows.forms.datagridviewcolumn.displayindex.aspx

DataGridViewColumn Properties

http://msdn.microsoft.com/en-us/library/system.windows.forms.datagridviewcolumn_properties.aspx

If I misunderstood you, or you have further questions, please feel free to tell me.

Best regards,

Ling Wang

---

Please remember to click “Mark as Answer�on the post that helps you, and to click “Unmark as Answer�if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.