Get data from the row of a Dropdown in a Gridview - asp.net

Question

I have a Gridview with a column that has a DropDownList.
I've binded this Dropdownlist with an event on the "SelectedIndexChanged".
The problem is i can't get the value of a label of another column in the same row.
The code is the next:
protected void grid_OnSelectedIndexChanged(object sender, EventArgs e)
{
grdCredenciales.DataBind();
var dropdown = (DropDownList)sender;
var row = (GridViewRow)dropdown.NamingContainer;
var label = (Label)row.FindControl("lblMatricula");
var value = label.Text; // I get "" in this line.
}
And in the grid i have:
<asp:ObjectDataSource ID="CredencialesDS" runat="server" />
<asp:GridView ID="grdCredenciales" runat="server" BackColor="White" DataSourceID="CredencialesDS"
CssClass="DDGridView" RowStyle-CssClass="td" HeaderStyle-CssClass="th" CellPadding="6" AllowSorting="True"
AllowPaging="True" AutoGenerateColumns="False" PageSize="10" OnRowDataBound="grdCredenciales_OnRowDataBound">
<Columns>
<asp:TemplateField>
<HeaderTemplate>
<asp:Label ID="Label7" ToolTip="Matrícula" runat="server" Text="Matrícula"/>
</HeaderTemplate>
<HeaderStyle HorizontalAlign="Left" Width="15%"/>
<ItemStyle HorizontalAlign="Left" />
<ItemTemplate>
<asp:Label ID="lblMatricula" runat="server"><%# Eval("Matricula") %></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField>
<HeaderTemplate>
<asp:Label ID="Label19" ToolTip="Estado" runat="server" Text="Estado" />
</HeaderTemplate>
<HeaderStyle HorizontalAlign="Left" Width="15%"/>
<ItemStyle HorizontalAlign="Left" />
<ItemTemplate>
<asp:DropDownList runat="server" ID="dpEstadoCredencial" AutoPostBack="True" OnSelectedIndexChanged="grid_OnSelectedIndexChanged" CssClass="comboEstado"/>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
I don't know why, but label.text returns an empty string. As you can see, i am calling the DataBind before, so the label should have a value at this point.
Do you know how can i get the value i need from the label in another column?
Thanks for everyone.

Answer 1

Check the GridView's DataSource before you do the DataBind(). Since you're missing the full ASPX markup, I'm not sure if you're setting the data source programmatically or with a SqlDataSource.
In any case, what will happen often with programmatically-set Data Sources is that they disappear on a PostBack, and when you call that DataBind, you're really DataBinding it to null, which would explain why you're getting string.Empty ("") for the Label's Text property.

Answer 2

Just verified the code provided by you. It's working completely.
Please make sure in the RowDataBound event of Grid View, you reattach the dropdownlist's SelectedIndexChanged event as below:
protected void CustomersGridView_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (Page.IsPostBack)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
DropDownList ddl = e.Row.FindControl("dropdown1") as DropDownList;
if (ddl != null)
{
ddl.SelectedIndexChanged += new EventHandler(CustomersGridView_SelectedIndexChanged);
}
}
}
}
Also, I used the same code as yours in SelectedIndexChanged event. I'm putting here my aspx Markup:
<asp:gridview id="CustomersGridView"
datasourceid="CustomersSqlDataSource"
autogeneratecolumns="false"
runat="server"
OnRowDataBound="CustomersGridView_RowDataBound">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:Label runat="server" ID="Label2" Text='<%# Bind("ID") %>' />
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField>
<ItemTemplate>
<asp:DropDownList ID="dropdown1" runat="server" AutoPostBack="true" OnSelectedIndexChanged="dropdown1_SelectedIndexChanged">
<asp:ListItem Text="Cat"></asp:ListItem>
<asp:ListItem Text="dog"></asp:ListItem>
<asp:ListItem Text="Mouse"></asp:ListItem>
<asp:ListItem Text="pig"></asp:ListItem>
<asp:ListItem Text="snake"></asp:ListItem>
</asp:DropDownList>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:gridview>
Please provide your GridView markup too for checking.