LinqDataSource - Can you limit the amount of records returned?

Question

I\'d like to use a LinqDataSource control on a page and limit the amount of records returned. I know if I use code behind I could do something like this:

Answer 1

Yes and No.

No, you cannot limit the results within the LinqDataSource control. Because Linq uses deferred execution, the expectation is that the presentation control will do the recordset limits.

Yes, you can do this with a ListView control. The trick is to use the DataPager control within the LayoutTemplate, like so:

<LayoutTemplate>
  <div id="itemPlaceholder" runat="server" />
  <asp:DataPager ID="DataPager1" runat="server" PageSize="3">
  </asp:DataPager>            
</LayoutTemplate>

Normally, you would include controls inside the DataPager like first, last, next, and previous. But if you just make it empty, then you will only see the three results that you desire.

Hope this helps.

Answer 2

I had this same issue. The way I got round this was to use the Selecting event on the LinqDataSource and return the result manually.

e.g.

protected void lnqRecentOrder_Selecting(object sender, LinqDataSourceSelectEventArgs e)
{
    DataClassesDataContext dx = new DataClassesDataContext();
    e.Result = (from o in dx.Orders
                where o.CustomerID == Int32.Parse(Request.QueryString["CustomerID"])
                select o).Take(5);
}

Answer 3

protected void DocsData_Selecting(object sender, LinqDataSourceSelectEventArgs e)
{
    e.Arguments.MaximumRows = 5;
}

Answer 4

You could base your Linq query on a stored proc that only returns x number of rows using a TOP statement. Remember just because you can do all your DB code in Linq doesn't mean you should. Plus, you can tell Linq to use the same return type for the stored proc as the normal table, so all your binding will still work, and the return results will be the same type

Answer 5

You can put event Selecting of LinqDataSource:

protected void ldsLastEntries_Selecting(object sender, LinqDataSourceSelectEventArgs e)
{
    e.Arguments.MaximumRows = 10;
}

Answer 6

I know that if you use a paging repeater or gridview with the linqdatasource it will automatically optimize the number of results returned, but I'm also pretty sure in the datasource wizard you can go to advanced options and limit it to

SELECT TOP 3 FROM 

which should allow you to do what you need