Question

I am new to ASP.NET and currently having problem with dropdownlists in the DetailsView.

Exception error: System.InvalidOperationException: Databinding methods such as Eval(), XPath(), and Bind() can only be used in the context of a databound control.

I have this code my code behind to refresh the list for the dropdownlists in DetailsView

protected void ddlVendor_SelectedIndexChanged 
               (object sender, EventArgs e) 
{ 
    DropDownList ddlVendorBB = 
        (DropDownList)DetailsView1.FindControl("VendorBUName"); 

    if (ddlVendorBB != null) 
    { 
        Response.Write("SelectChanged"); 
        ddlVendorBB.DataBind(); 
    } 
} 

protected void SqlDataSourceProd_Selecting 
    (object sender, SqlDataSourceSelectingEventArgs e) 
{ 
    DropDownList ddlVendor = 
        (DropDownList)DetailsView1.FindControl("VendorName"); 

    if (ddlVendor != null) 
    { 
        e.Command.Parameters["@VendorID"].Value = ddlVendor.SelectedValue; 
    } 
}

These two dropdownlists in the DetailsView

<EditItemTemplate> 
    <asp:DropDownList id="VendorName"
        datasourceid="VendorSqlDataSource"
        AutoPostBack="true"
        datatextfield="VendorName"
        DataValueField="VendorID"   
        SelectedValue='<%# Bind("VendorID") %>'  
        runat="server"
        OnSelectedIndexChanged="ddlCategory_SelectedIndexChanged" />

    <asp:SqlDataSource ID="VendorSqlDataSource"
        ConnectionString="<%$Connectionstrings:ConnectionString%>" 
        SelectCommand="SELECT VendorID, VendorName from MDF_Vendor"
        runat="server"> 
    </asp:SqlDataSource> 
</EditItemTemplate> 


<EditItemTemplate>
    <asp:DropDownList id="VendorBUName"
        datasourceid="VendorBUSqlDataSource" 
        datatextfield="VendorBUName"
        DataValueField="VendorBUID"   
        SelectedValue='<%# Bind("VendorBUID") %>'  
        runat="server"/>

    <asp:SqlDataSource ID="VendorBUSqlDataSource"
        runat="server"
        ConnectionString="<%$Connectionstrings:ConnectionString%>"
        selectcommand="SELECT VendorBUID, VendorBUName
                       from MDF_VendorBU
                       Where VendorID = @VendorID"
        OnSelecting="SqlDataSourceProd_Selecting"> 
        <SelectParameters> 
            <asp:Parameter Name="VendorID" Type="Int32" /> 
        </SelectParameters> 
    </asp:SqlDataSource> 
</EditItemTemplate>

Problem is:

If I leave SelectedValue= there, the dropdownlists in Edit mode seletected the correct value in the items listed when I first click Edit, but when I select a new VendorName, it errors “Databining method such as Eval(), Xpath(), and Bind()… “.

Now, if I removed the Selectedvalued for the dropdownlists, it will work for refreshing the VendorBUName when select a new VendorName, but NOT not selected the default VendorID when I click “Edit”. It just list the VendorName list without selected the current VendorID one.

Can someone please let me know what wrong in my codes? Thanks!

Answer 1

As the error states, you cannot use Bind where you are trying to use it. You should be able to use the DataBinder though

SelectedValue='<%# DataBinder.Eval (Container.DataItem, "VendorBUID") %>'

---

Edit: Since binding a value to the SelectedValue with DataBinder didn’t work, you can try to set the value when binding data. Provided dataSource is some instance of a class that has a property called VendorBUID, something similar to this might work in

public override void OnLoad(EventArgs e) {
    VendorBUName.DataBinding += dataBindDropDown;
}

private void dataBindDropDown(object sender, EventArgs e) {
    VendorBUName.SelectedValue = dataSource.VendorBUID;
}