DropDownList.DataTextField不能绑定到数据集？

Question

I'm trying to bind a dataset to a dropdownlist , which throws a HttpException

Here's what I'm trying to do

if (dsGroupsNotOnFestival.Tables[0].Rows.Count > 0)
{
    //Bind dataset to new group selection
    ddlNewGroup.DataSource = dsGroupsNotOnFestival.Tables[0].DefaultView;
    ddlNewGroup.DataValueField = "band_id";
    ddlNewGroup.DataTextField = "band_naam";
    ddlNewGroup.DataBind();
}
else
{
    ddlNewGroup.Items.Add(new ListItem("No groups to add"));
}

The exception message:

DataBinding: 'System.Data.DataRowView' does not contain a property with the name 'band_naam'.

I'm absolutely positive that the dataset contains a column with the title band_naam. As you can see, the exception is thrown when binding the DataTextField , meaning that the DataValueField is bound correctly, right?

EDIT:

This is the stored procedure:

USE [groep2_festivals]
GO
/****** Object:  StoredProcedure [dbo].[GetGroupsOfFestival]    Script Date: 14-05-13 12:31:18 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author:      Robbie Vercammen
-- Create date: 2013-05-09
-- Description: Getting all groups for a defined festival
-- =============================================
ALTER PROCEDURE [dbo].[GetGroupsOfFestival]
    (
    @festId  nvarchar(4)
    )
AS
BEGIN
    DECLARE @query varchar(255)

    SELECT b.*, p.* 
    FROM bands b 
    JOIN bandsperfestival bpf ON b.band_id = bpf.band_id 
    JOIN podia p ON p.pod_id = bpf.pod_id WHERE fest_id LIKE @festId
    EXEC(@query)
END

Notice the b.* and bands b ? Now here that table:

This stored procedure has been used on multiple occasions, so I'm pretty sure that it works correctly. But here's perhaps the most important code that I forgot to mention:

//Filling dataset with groups not on this festival
dsGroupsNotOnFestival.Tables.Add(new DataTable());
foreach (DataRow row in dsGroupsAll.Tables[0].Rows)
{
    if (!dsGroupsPerFestival.Tables[0].Rows.Equals(row))
    {
        dsGroupsNotOnFestival.Tables[0].ImportRow(row);
    }
}

And once again, the DataSet dsGroupsAll has been used before so the data is present :)

@manish mishra dsGroupsAll is filled with the same stored procedure above. To prove that there is actually data in there:

For those still following, I've confirmed that there are 14 rows in dsGroupsNotOnFestival . When i'm trying to get a value in a simple way, for example:

String strResult = dsGroupsNotOnFestival.Tables[0].Rows[0][0].ToString();

I get an exception saying that column 0 could not be found... why is that?

Answer 1

I'm absolutely positive that the dataset contains a column with the title band_naam.

I understand how you feel, but I'm absolutely positive that there isn't one because that error is extremely explicit:

does not contain a property with the name 'band_naam'

Have another look at the code that fills that DataSet . The DefaultView is a perfect image of the DataTable , which of course is the result set of your query, so the query you're using to fill this DataTable is missing this field.

Maybe it's a calculated field and you forgot the AS keyword to give it a column name.

---

EDIT

Based on your feedback (ie screenshots of the queries and schema), I'm going to say Habib probably hit it right on the head in the comments, change this line:

ddlNewGroup.DataSource = dsGroupsNotOnFestival.Tables[0].DefaultView;

to this line:

ddlNewGroup.DataSource = dsGroupsNotOnFestival.Tables[0];

I personally have never had a problem binding to a DefaultView but I don't feel there are any other possibilities left.

Answer 2

Not sure if I am allowed to approve my own answers, but I found the solution to my nightmare.

//Filling dataset with groups not on this festival
dsGroupsNotOnFestival = dsGroupsPerFestival.Clone();
foreach (DataRow row in dsGroupsAll.Tables[0].Rows)
{
    if (!dsGroupsPerFestival.Tables[0].Rows.Equals(row))
    {
        dsGroupsNotOnFestival.Tables[0].ImportRow(row);
    }
}

The difference is, I'm cloning the original DataSet preserving the structure, constraints, etc using:

dsGroupsPerFestival.Clone()

Thanks everyone for helping me out!