GridView control - paging with linq. Where is objectDataSource?

Question

I have visual web part with custom logic which retrieves me strongly typed list (not SPList -> .NET list object) which than I bind to gridview which has paging enabled. That works fine. Problem is: PAGING. When I use

public static IEnumerable<TSource> Page<TSource>(this IEnumerable<TSource> source, int page, int pageSize)
{
                return source.Skip((page - 1) * pageSize).Take(pageSize);
} 

i get data subset. When I bind it to gridview, data show correctly but i loose real page count (all items) which i need for gridview page indicator. Normally I would use objectDataSource(with appropriate method for all items count, and method for paging) BUT surprise: It's not enabled for visual webpart and I can't add it to the page. I looked here on the site, also googled, but I can't find some good, simple and useful solution to solve my problem.

PLEASE any useful suggestion will be greatly appreciated!

Answer 1

You are doing the paging yourself, which means the GridView isn't aware of all the items so it doesn't display the count. I would recommend letting the GridView handle the paging using ObjectDataSource like you mention.

I'm not sure if you're using a normal GridView or SPGridView.. but take a look at this good tutorial Building A SPGridView Control – Part 1: Introducing the SPGridView. This makes it easy because you just add the pager and connect it to your grid programmatically:

SPGridViewPager pager = new SPGridViewPager();
pager.GridViewId = grid.ID;

Alternatively, you could just write your own paging code and generate the pages yourself.

---

*Edit*

Here is a simple example.

// goes in SimpleGridView.cs
class SimpleGridView : CompositeControl
{
    private ObjectDataSource _gridDS;
    private GridView _grid;

    public DataTable SelectData()
    {
        DataTable dataSource = new DataTable();

        // setup columns
        dataSource.Columns.Add("ID", Type.GetType("System.Int32"));
        dataSource.Columns.Add("Name");
        dataSource.Columns.Add("Region");
        dataSource.Columns.Add("Total Sales", Type.GetType("System.Double"));
        dataSource.Columns.Add("Created", Type.GetType("System.DateTime"));

        // add some bogus data
        dataSource.Rows.Add(1, "J. Smith", "Europe", 10000, new DateTime(2010, 10, 7, 8, 0, 0));
        dataSource.Rows.Add(2, "J. Smith", "North America", 15000, new DateTime(2010, 10, 8, 9, 00, 0));
        dataSource.Rows.Add(3, "J. Smith", "Asia", 5000, new DateTime(2010, 10, 7, 10, 0, 0));
        dataSource.Rows.Add(4, "S. Jones", "Europe", 7000, new DateTime(2010, 10, 9, 11, 0, 0));
        dataSource.Rows.Add(5, "S. Jones", "North America", 30000, new DateTime(2010, 10, 7, 9, 00, 0));
        dataSource.Rows.Add(6, "S. Jones", "Asia", 8700, new DateTime(2010, 10, 9, 8, 0, 0));
        dataSource.Rows.Add(7, "W. Nguyen", "Europe", 3000, new DateTime(2010, 10, 8, 8, 0, 0));
        dataSource.Rows.Add(8, "W. Nguyen", "North America", 50000, new DateTime(2010, 10, 7, 12, 30, 0));
        dataSource.Rows.Add(9, "W. Nguyen", "Asia", 25000, new DateTime(2010, 10, 7, 8, 0, 0));
        dataSource.Rows.Add(10, "C. O'Reilly", "Europe", 200, new DateTime(2008, 1, 16, 15, 0, 0));
        dataSource.Rows.Add(11, "C. O'Reilly", "North America", 5000, new DateTime(2009, 11, 1, 16, 0, 0));
        dataSource.Rows.Add(12, "C. O'Reilly", "Asia", 8000, new DateTime(2010, 10, 9, 19, 0, 0));

        return dataSource;
    }

    private void GenerateColumns()
    {
        AddBoundField("ID");
        AddBoundField("Name");
        AddBoundField("Region");
        AddBoundField("Total Sales");
        AddBoundField("Created");
    }

    private void AddBoundField(string name)
    {
        BoundField column = new BoundField();
        column.DataField = name;
        column.SortExpression = name;
        column.HeaderText = name;
        _grid.Columns.Add(column);
    }

    protected sealed override void CreateChildControls()
    {
        const string GRIDID = "grid";
        const string DATASOURCEID = "gridDS";

        // initialize the ODS
        _gridDS = new ObjectDataSource();
        _gridDS.ID = DATASOURCEID;
        // calling our SelectData function in this CompositeControl
        _gridDS.SelectMethod = "SelectData";
        _gridDS.TypeName = this.GetType().AssemblyQualifiedName;
        _gridDS.ObjectCreating += new ObjectDataSourceObjectEventHandler(gridDS_ObjectCreating);

        this.Controls.Add(_gridDS);

        // Initialize the grid and link it to the ObjectDataSource
        _grid = new GridView();
        _grid.ID = GRIDID;
        _grid.DataSourceID = _gridDS.ID;
        _grid.AutoGenerateColumns = false;

        // Paging
        _grid.AllowPaging = true;
        _grid.PageSize = 10;

        // Sorting
        _grid.AllowSorting = true;

        this.Controls.Add(_grid);

        GenerateColumns();

        // setting PagerTemplate to null here will display page numbers for paging
        _grid.PagerTemplate = null;
    }

    private void gridDS_ObjectCreating(object sender, ObjectDataSourceEventArgs e)
    {
        // our ObjectDataSource uses this CompositeControl to select data
        e.ObjectInstance = this;
    }
}

This goes in your web part class:

protected override void CreateChildControls()
{
    base.CreateChildControls();

    SimpleGridView grid = new SimpleGridView();
    this.Controls.Add(grid);
}