Gridview row editing - dynamic binding to a DropDownList - asp.net

Question

I'm trying to get an ASP.NET 3.5 GridView to show a selected value as string when being displayed, and to show a DropDownList to allow me to pick a value from a given list of options when being edited. Seems simple enough?
My gridview looks like this (simplified):
<asp:GridView ID="grvSecondaryLocations" runat="server"
DataKeyNames="ID" OnInit="grvSecondaryLocations_Init"
OnRowCommand="grvSecondaryLocations_RowCommand"
OnRowCancelingEdit="grvSecondaryLocations_RowCancelingEdit"
OnRowDeleting="grvSecondaryLocations_RowDeleting"
OnRowEditing="grvSecondaryLocations_RowEditing"
OnRowUpdating="grvSecondaryLocations_RowUpdating" >
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:Label ID="lblPbxTypeCaption" runat="server"
Text='<%# Eval("PBXTypeCaptionValue") %>' />
</ItemTemplate>
<EditItemTemplate>
<asp:DropDownList ID="ddlPBXTypeNS" runat="server"
Width="200px"
DataTextField="CaptionValue"
DataValueField="OID" />
</EditItemTemplate>
</asp:TemplateField>
</asp:GridView>
The grid gets displayed OK when not in editing mode - the selected PBX type shows its value in the asp:Label control. No surprise there.
I load the list of values for the DropDownList into a local member called _pbxTypes in the OnLoad event of the form. I verified this - it works, the values are there.
Now my challenge is: when the grid goes into editing mode for a particular row, I need to bind the list of PBX's stored in _pbxTypes.
Simple enough, I thought - just grab the drop down list object in the RowEditing event and attach the list:
protected void grvSecondaryLocations_RowEditing(object sender, GridViewEditEventArgs e)
{
grvSecondaryLocations.EditIndex = e.NewEditIndex;
GridViewRow editingRow = grvSecondaryLocations.Rows[e.NewEditIndex];
DropDownList ddlPbx = (editingRow.FindControl("ddlPBXTypeNS") as DropDownList);
if (ddlPbx != null)
{
ddlPbx.DataSource = _pbxTypes;
ddlPbx.DataBind();
}
.... (more stuff)
}
Trouble is - I never get anything back from the FindControl call - seems like the ddlPBXTypeNS doesn't exist (or can't be found).
What am I missing?? Must be something really stupid.... but so far, all my Googling, reading up on GridView controls, and asking buddies hasn't helped.
Who can spot the missing link? ;-)

Answer 1

Quite easy... You're doing it wrong, because by that event the control is not there:
protected void gv_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow &&
(e.Row.RowState & DataControlRowState.Edit) == DataControlRowState.Edit)
{
// Here you will get the Control you need like:
DropDownList dl = (DropDownList)e.Row.FindControl("ddlPBXTypeNS");
}
}
That is, it will only be valid for a DataRow (the actually row with data), and if it's in Edit mode... because you only edit one row at a time. The e.Row.FindControl("ddlPBXTypeNS") will only find the control that you want.

Answer 2

I am using a ListView instead of a GridView in 3.5. When the user wants to edit I have set the selected item of the dropdown to the exising value of that column for the record. I am able to access the dropdown in the ItemDataBound event. Here's the code:
protected void listViewABC_ItemDataBound(object sender, ListViewItemEventArgs e)
{
// This stmt is used to execute the code only in case of edit
if (((ListView)(sender)).EditIndex != -1 && ((ListViewDataItem)(e.Item)).DisplayIndex == ((ListView)(sender)).EditIndex)
{
((DropDownList)(e.Item.FindControl("ddlXType"))).SelectedValue = ((MyClass)((ListViewDataItem)e.Item).DataItem).XTypeId.ToString();
((DropDownList)(e.Item.FindControl("ddlIType"))).SelectedValue = ((MyClass)((ListViewDataItem)e.Item).DataItem).ITypeId.ToString();
}
}

Answer 3

protected void grvSecondaryLocations_RowEditing(object sender, GridViewEditEventArgs e)
{
grvSecondaryLocations.EditIndex = e.NewEditIndex;
DropDownList ddlPbx = (DropDownList)(grvSecondaryLocations.Rows[grvSecondaryLocations.EditIndex].FindControl("ddlPBXTypeNS"));
if (ddlPbx != null)
{
ddlPbx.DataSource = _pbxTypes;
ddlPbx.DataBind();
}
.... (more stuff)
}

Answer 4

You can use SelectedValue:
<EditItemTemplate>
<asp:DropDownList ID="ddlPBXTypeNS"
runat="server"
Width="200px"
DataSourceID="YDS"
DataTextField="CaptionValue"
DataValueField="OID"
SelectedValue='<%# Bind("YourForeignKey") %>' />
<asp:YourDataSource ID="YDS" ...../>
</EditItemTemplate>

Answer 5

The checked answer from balexandre works great. But, it will create a problem if adapted to some other situations.
I used it to change the value of two label controls - lblEditModifiedBy and lblEditModifiedOn - when I was editing a row, so that the correct ModifiedBy and ModifiedOn would be saved to the db on 'Update'.
When I clicked the 'Update' button, in the RowUpdating event it showed the new values I entered in the OldValues list. I needed the true "old values" as Original_ values when updating the database. (There's an ObjectDataSource attached to the GridView.)
The fix to this is using balexandre's code, but in a modified form in the gv_DataBound event:
protected void gv_DataBound(object sender, EventArgs e)
{
foreach (GridViewRow gvr in gv.Rows)
{
if (gvr.RowType == DataControlRowType.DataRow && (gvr.RowState & DataControlRowState.Edit) == DataControlRowState.Edit)
{
// Here you will get the Control you need like:
((Label)gvr.FindControl("lblEditModifiedBy")).Text = Page.User.Identity.Name;
((Label)gvr.FindControl("lblEditModifiedOn")).Text = DateTime.Now.ToString();
}
}
}

Answer 6

<asp:GridView ID="GridView1" runat="server" PageSize="2" AutoGenerateColumns="false"
AllowPaging="true" BackColor="White" BorderColor="#CC9966" BorderStyle="None"
BorderWidth="1px" CellPadding="4" OnRowEditing="GridView1_RowEditing" OnRowUpdating="GridView1_RowUpdating"
OnPageIndexChanging="GridView1_PageIndexChanging" OnRowCancelingEdit="GridView1_RowCancelingEdit"
OnRowDeleting="GridView1_RowDeleting">
<FooterStyle BackColor="#FFFFCC" ForeColor="#330099" />
<RowStyle BackColor="White" ForeColor="#330099" />
<SelectedRowStyle BackColor="#FFCC66" Font-Bold="True" ForeColor="#663399" />
<PagerStyle BackColor="#FFFFCC" ForeColor="#330099" HorizontalAlign="Center" />
<HeaderStyle BackColor="#990000" Font-Bold="True" ForeColor="#FFFFCC" />
<Columns>
<asp:TemplateField HeaderText="SerialNo">
<ItemTemplate>
<%# Container .DataItemIndex+1 %>.&nbsp
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="RollNo">
<ItemTemplate>
<%--<asp:Label ID="lblrollno" runat="server" Text='<%#Eval ("RollNo")%>'></asp:Label>--%>
<asp:TextBox ID="txtrollno" runat="server" Text='<%#Eval ("RollNo")%>'></asp:TextBox>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="SName">
<ItemTemplate>
<%--<asp:Label ID="lblsname" runat="server" Text='<%#Eval("SName")%>'></asp:Label>--%>
<asp:TextBox ID="txtsname" runat="server" Text='<%#Eval("SName")%>'> </asp:TextBox>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="C">
<ItemTemplate>
<%-- <asp:Label ID="lblc" runat="server" Text='<%#Eval ("C") %>'></asp:Label>--%>
<asp:TextBox ID="txtc" runat="server" Text='<%#Eval ("C") %>'></asp:TextBox>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Cpp">
<ItemTemplate>
<%-- <asp:Label ID="lblcpp" runat="server" Text='<%#Eval ("Cpp")%>'></asp:Label>--%>
<asp:TextBox ID="txtcpp" runat="server" Text='<%#Eval ("Cpp")%>'> </asp:TextBox>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Java">
<ItemTemplate>
<%-- <asp:Label ID="lbljava" runat="server" Text='<%#Eval ("Java")%>'> </asp:Label>--%>
<asp:TextBox ID="txtjava" runat="server" Text='<%#Eval ("Java")%>'> </asp:TextBox>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Edit" ShowHeader="False">
<EditItemTemplate>
<asp:LinkButton ID="lnkbtnUpdate" runat="server" CausesValidation="true" Text="Update"
CommandName="Update"></asp:LinkButton>
<asp:LinkButton ID="lnkbtnCancel" runat="server" CausesValidation="false" Text="Cancel"
CommandName="Cancel"></asp:LinkButton>
</EditItemTemplate>
<ItemTemplate>
<asp:LinkButton ID="btnEdit" runat="server" CausesValidation="false" CommandName="Edit"
Text="Edit"></asp:LinkButton>
</ItemTemplate>
</asp:TemplateField>
<asp:CommandField HeaderText="Delete" ShowDeleteButton="True" ShowHeader="True" />
<asp:CommandField HeaderText="Select" ShowSelectButton="True" ShowHeader="True" />
</Columns>
</asp:GridView>
<table>
<tr>
<td>
<asp:Label ID="lblrollno" runat="server" Text="RollNo"></asp:Label>
<asp:TextBox ID="txtrollno" runat="server"></asp:TextBox>
</td>
<td>
<asp:Label ID="lblsname" runat="server" Text="SName"></asp:Label>
<asp:TextBox ID="txtsname" runat="server"></asp:TextBox>
</td>
<td>
<asp:Label ID="lblc" runat="server" Text="C"></asp:Label>
<asp:TextBox ID="txtc" runat="server"></asp:TextBox>
</td>
<td>
<asp:Label ID="lblcpp" runat="server" Text="Cpp"></asp:Label>
<asp:TextBox ID="txtcpp" runat="server"></asp:TextBox>
</td>
<td>
<asp:Label ID="lbljava" runat="server" Text="Java"></asp:Label>
<asp:TextBox ID="txtjava" runat="server"></asp:TextBox>
</td>
</tr>
<tr>
<td>
<asp:Button ID="Submit" runat="server" Text="Submit" OnClick="Submit_Click" />
<asp:Button ID="Reset" runat="server" Text="Reset" OnClick="Reset_Click" />
</td>
</tr>
</table>