What does the data source need to have for a GridView to autogenerate columns?

Question

I created custom datatype classes that format the data the way I need it. The data I retrieve from the database comes as .NET base types, so I need to loop through the DataTable, convert each item into it's custom type, and put the converted item into a new table. I also copy the column names from the old table to the new one. The problem is, when I bind a GridView to my new table, it throws an exception:

HttpException:  
The data source for GridView with id 'TestGrid' did not have any properties
or attributes from which to generate columns.  Ensure that your data source 
has content.  

Stack Trace:
at System.Web.UI.WebControls.GridView.CreateAutoGeneratedColumns(PagedDataSource dataSource)
at System.Web.UI.WebControls.GridView.CreateColumns(PagedDataSource dataSource, Boolean useDataSource)
at System.Web.UI.WebControls.GridView.CreateChildControls(IEnumerable dataSource, Boolean dataBinding)
at System.Web.UI.WebControls.CompositeDataBoundControl.PerformDataBinding(IEnumerable data)
at System.Web.UI.WebControls.GridView.PerformDataBinding(IEnumerable data)
at System.Web.UI.WebControls.DataBoundControl.OnDataSourceViewSelectCallback(IEnumerable data)
at System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback)
at System.Web.UI.WebControls.DataBoundControl.PerformSelect()
at System.Web.UI.WebControls.BaseDataBoundControl.DataBind()
at System.Web.UI.WebControls.GridView.DataBind()

What do I need to add to my DataTable to get autogeneratecolumns to work?

Edit: Here is the code for the DataTable:

     // Populate first DataTable with data from database.
     adapter = new DataAdapter("SELECT status, date_ordered, date_due FROM import_table", OpenConnection);
     DataTable originalTable = new DataTable();
     adapter.Fill(originalTable)

     // Second DataTable for converted table data.
     DataTable convertedTable = new DataTable();

     // The list of custom datatypes to convert to.
     Type[] newTypes = {typeof(TrackingStatus), typeof(Date), typeof(Date)};

     // Set the ColumnName and DataType on each column of the new table.
     for(int i = 0; i < originalTable.Columns.Count; i++)
     {
        convertedTable.Columns.Add();
        convertedTable.Columns[i].ColumnName = originalTable.Columns[i].ColumnName;
        if(newTypes.Length > i)
           convertedTable.Columns[i].DataType = newTypes[i];
     }

     // Convert each item from the old table and add it to the new table.
     foreach(DataRow oldRow in originalTable.Rows)
     {
        DataRow newRow = convertedTable.NewRow();

        for(int i = 0; i < convertedTable.Columns.Count; i++)
        {
           if(newTypes.Length <= i)
              newRow[i] = oldRow[i];
           else if(newTypes[i] == typeof(Date))
              newRow[i] = Date.FromObject(oldRow[i]);
           else if(newTypes[i] == typeof(TrackingStatus))
              newRow[i] = TrackingStatus.FromObject(oldRow[i]);
           else if(newTypes[i] == typeof(EmailAddress))
              newRow[i] = EmailAddress.FromObject(oldRow[i]);
        }

        convertedTable.Rows.Add(newRow);
     }

     // Bind the GridView.
     displayGrid.DataSource = convertedTable;
     displayGrid.DataBind();

In fact, instead of copiying your data into a DataTable, couldn't you use a List of your CustomType? — Francis P, Dec 07 '12 at 16:35

score 1 · Answer 1 · answered Dec 07 '12 at 16:31

1

Your custom type needs public properties like these:

public class Foo
{
    public int Id;
    public string Name;
}

or you need to use the DataTable itself as DataSource.

answered Dec 07 '12 at 16:31

Tim Schmelter

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I _am_ using the DataTable as DataSource. The custom types are inside it. – Boric Dec 07 '12 at 16:33
@Boric: Why do you use a custom type in the DataTable. I would avoid it if possible. Either use a `DataTable` or a `List`. – Tim Schmelter Dec 07 '12 at 16:39
My site has many pages which retrieve and display different database queries. I am using a custom Date object etc. that knows how to format itself so that I don't duplicate the formatting code in each page. I am not intending on creating a custom type for each query. – Boric Dec 07 '12 at 17:06

Azhar Khorasany · Accepted Answer · 2012-12-07T17:33:02.390

Instead of creating a new datatable when you convert each to custom types, create a new List and bind the list to the datasource. e.g.

var list = new List<MyClass>();

var myType = //Convert your type
list.Add(myType);

grid.DataSource = list;

And ofcourse this all is just an idea of how to do it.

UPDATE: Saw your code afterwards:

Try this:

Create a class called ImportRow

class ImportRow
{
    private string m_Status = string.Empty;
    private DateTime m_DateOrdered;
    private DateTime m_DateDue;

    public ImportRow() { }

    public string Status
    {
        get { return m_Status; }
        set { m_Status = value; }
    }

    public DateTime DateOrdered
    {
        get { return m_DateOrdered; }
        set { m_DateOrdered = value; }
    }

    public DateTime DateDue
    {
        get { return m_DateDue; }
        set { m_DateDue = value; }
    }

}

Then use it as:

        var importedData = new List<ImportRow>();

        foreach (DataRow oldRow in originalTable.Rows)
        {
            var newRow = new ImportRow();

            newRow.Status = oldRow["status"].ToString();
            newRow.DateDue = Convert.ToDateTime(oldRow["date_due"].ToString());
            newRow.DateOrdered = Convert.ToDateTime(oldRow["date_ordered"].ToString());

            importedData.Add(newRow);
        }

Then

 displayGrid.DataSource = importedData;
 displayGrid.DataBind();

A list won't work because I have multiple columns. Besides, I don't see how that solves the problem. — Boric, Dec 07 '12 at 16:57
See my comment [here](http://stackoverflow.com/questions/13766980/what-does-the-data-source-need-to-have-for-a-gridview-to-autogenerate-columns/13767224#comment18926250_13767103). — Boric, Dec 07 '12 at 18:52

What does the data source need to have for a GridView to autogenerate columns?

2 Answers2