Why is the DataBind() method necessary?

Question

Simple question, I guess.

For a long time I\'ve blindly followed a (supposedly) common pattern when programmatically databinding my ASP.NET controls. Namely:

Answer 1

DataSource is a property of the BaseDataBoundControl class. DataSourceID is a property of the DataBoundControl class, which inherits from BaseDataBoundControl and did not exist before ASP.NET 2.0.

Since DataBoundControl is explicitly for displaying data in a list or tabular form, and BaseDataBoundControl cannot make that assumption, binding is not automatic when DataSource is set because the type of control may not match the structure of the data.

Of course, this is all just a guess based on the MSDN documentation, so I could be wrong.

Answer 2

Try this:

if (GridView1.EditIndex == e.Row.RowIndex)
{              
    TextBox t2 = (TextBox)e.Row.FindControl("TextBox2");
    DateTime dt2;
    if (DateTime.TryParse(t2.Text, out dt2))
    {
        t2.Text = dt2.ToString("yyyy-MM-dd");
    }
}

Answer 3

In ASP.Net, it's often important to have certain data available and ready at certain points in the page life cycle, and not before. For example, you may need to bind to a drop down list early to allow setting the selected index on that list later. Or you might want to wait a bit to bind that large grid to reduce the amount of time you hold that connection active/keep the data in memory.

Having you explicitly call the .DataBind() method makes it possible to support scenarios at both ends of the spectrum.

Answer 4

I noticed that without using DataBind() that nothing will be displayed in my GridView so I always include it as shown in this section of code:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

    ' TableAdapter object.
    ' Provide communication between this application and the database.
    '-----------------------------------------------------------------
    Dim suppliersAdapter As New SuppliersTableAdapter

    ' Get the data from the TableAdapter into the GridView.
    '------------------------------------------------------
    GridView1.DataSource = suppliersAdapter.GetSuppliers()

    ' Display the result set from the TableAdapter in the GridView.
    '--------------------------------------------------------------
    GridView1.DataBind()
End Sub

Please forgive the extra commenting as I'm also still learning ASP.Net as well and the comments will help me learn better "what and why" to use certain statements.