使用 C# 和实体框架在 ASP.NET 中加载 GridView

Question

I tried loading a DataGridView with data from server and the code I wrote is saying the data source is null during debugging.

protected void ViewData_Load(object sender, EventArgs e)
{
    using (var files = new DBEntitiesModelConn())
    {
        var ViewData= from i in files.LicenseApplicationCPs
                              select new
                                  {
                                      Name = i.Name,
                                      Status = i.Status,
                                      Date = i.DateSubmitted,
                                  };
        ViewDataGrid.DataSource = ViewData.ToList();
    }
}

The datasource is saying is null.

Answer 1

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.

protected void ViewData_Load(object sender, EventArgs e)
{
    using (var files = new DBEntitiesModelConn())
    {
        var ViewData= from i in files.LicenseApplicationCPs
                              select new
                                  {
                                      Name = i.Name,
                                      Status = i.Status,
                                      Date = i.DateSubmitted,
                                  };
        ViewDataGrid.DataSource = ViewData.ToList();
        ViewDataGrid.DataBind();
    }
}