Question

how do you properly call methods inside custom binding expressions? Are there complications because the dropdownlist is inside a detailsview?

asp.net code:

<asp:DropDownList ID="ddlExceptionEditStatus" runat="server"
      DataSourceID="odsExceptionsStatus"
      DataTextField="Name"
      DataValueField="StatusID"
      SelectedValue='<%# Bind("StatusID") %>' 
      BackColor="<%# SetBackColorProp(Container.DataItem) %>">
 </asp:DropDownList>

code behind:

protected System.Drawing.Color SetBackColorProp(object o)
{
    System.Drawing.Color statusColor = System.Drawing.Color.White;
    string statusName = o as string;
    if (statusName != null)
    {
        statusColor = System.Drawing.ColorTranslator.FromHtml(FISBLL.StatusColors.GetColor(statusName));
        return statusColor;
    }
    else
    {
        return statusColor;
    }        
}

Doesn’t change the backcolor. but doesn’t throw an exception.

Answer 1

So, I had two mistakes:

1) I needed to cast the Container.DataItem to the class object i was using for the ObjectDataSource. After casting, the BackColor for each item in the dropdownlist matched the StatusID of the casted Container.DataItem.

2) Unfortunately this gave all the items the same color, where as I wanted each item’s color to reflect the their own value attached to the dropdownlist. This is because the dropdownlist has an objectdatasource outside the DetailsView that it’s inside of. Therefor the selectedValue item of the dropdownlist dictated the colors for all the other items.

I decided to go with Tim’s suggestion and tie the BackColor setting for each item in the databound event:

protected string GetColor(string name)
{
    return FISBLL.StatusColors.GetColor(name);
}

protected void ddlExceptionEditStatus_DataBound(object sender, EventArgs e)
{
    foreach (ListItem item in ((DropDownList)sender).Items)
    {
        item.Attributes.Add("style", "background-color:" + GetColor(item.Text));
    }

}

And the correct behavior is shown: