将控件绑定到LINQ查询-找不到字段

Question

I have several controls that I am trying to bind to LINQ queries but am getting the following error:

$exception {"DataBinding: 'System.Data.DataRow' does not contain a property with the name 'Key'."} System.Exception {System.Web.HttpException}

I'm binding it the following way:

    myDropDownList.DataSource = myDataTable.AsEnumerable().Where(
                        r => ((string) r["ColumnName"]) == "ColumnIWant").ToList()
myDropDownList.DataTextField = "Key";
myDropDownList.DataValueField = "Value";

I have tried this both with and without the .ToList(), as suggested in other answers but with no effect.

"myDataTable" has both columns "Key" and "Value" . It was my understanding you could bind this way, but I seem to be missing a step in specifying the property names.

Answer 1

My suggestion (as it has worked to me this way with GridView and DropDownList controls), is that you specify this DataTextField and DataValueField properties in the design file (aspx) like this:

<asp:DropDownList ID="DropDownList1" runat="server" 
                  DataTextField="Key" DataValueField="Value">
</asp:DropDownList>

This way, you can still apply the ToList() function to the DataTable and it will work (tested).

If if doesn't, maybe you need to set up one break-point after filling up your myDataTable and another one after the LINQ query, to check if the "Key" and "Value" columns are still there.

Answer 2

If it defenitely contains values for key and Value in the data table then i suggest you to use like the following :

myDropDownList.DataSource = myDataTable.AsEnumerable().Where(
                    r => (r.Field<string>("ColumnName")) == "ColumnIWant").ToList<DataRow>();
myDropDownList.DataTextField = "Key";
myDropDownList.DataValueField = "Value";

I had changed ToList() to .ToList<DataRow>(); so that the datasourse can find the key and value as same as from a datatable, and change the comparison like this: r.Field<string>("ColumnName")

Answer 3

Using .CopyToDataTable() works for what I'm trying to do, but I'd still prefer to know how to bind the data directly to the EnumerableRows collection if that's possible.

Here is what I did:

myDropDownList.DataSource = myDataTable.AsEnumerable().Where(
                        r => ((string) r["ColumnName"]) == "ColumnIWant").CopyToDataTable();
myDropDownList.DataTextField = "Key";
myDropDownList.DataValueField = "Value";