Cant Get Data To Return To My Grid View Using Linq in ASP.NET - asp.net

Question

Not sure why but i cant get my data to return. It starts out saying there is not data records to display. But when i select the month and year of the information i am looking for the grid view disappears. Any suggestions
NutritionEntities context;
protected void Page_Load(object sender, EventArgs e)
{
context = new NutritionEntities();
if (!IsPostBack)
{
for (int i = DateTime.Now.Year; i > 1988; i--)
{
ddlYear.Items.Add(new ListItem(i.ToString(), i.ToString()));
}
int selectedMonth = int.Parse(ddlMonth.SelectedValue);
int selectedYear = int.Parse(ddlYear.SelectedValue);
GridView1.DataSource =
from exercise in context.Exercises
where exercise.exerciseDate.Value.Month == selectedMonth && exercise.exerciseDate.Value.Year == selectedYear
select new
{
exercise.exerciseDate,
exercise.duration,
exercise.caloriesBurned,
exercise.averageHR,
exercise.distanceInMiles,
exercise.notes
};
GridView1.DataBind();
}
}
protected void ddlMonth_SelectedIndexChanged(object sender, EventArgs e)
{
int selectedMonth = int.Parse(ddlMonth.SelectedValue);
int selectedYear = int.Parse(ddlYear.SelectedValue);
GridView1.DataSource =
from exercise in context.Exercises
where exercise.exerciseDate.Value.Month == selectedMonth && exercise.exerciseDate.Value.Year == selectedYear
select new
{
exercise.exerciseDate,
exercise.duration,
exercise.caloriesBurned,
exercise.averageHR,
exercise.distanceInMiles,
exercise.notes
};
GridView1.DataBind();
}
protected void ddlYear_SelectedIndexChanged(object sender, EventArgs e)
{
int selectedMonth = int.Parse(ddlMonth.SelectedValue);
int selectedYear = int.Parse(ddlYear.SelectedValue);
GridView1.DataSource =
from exercise in context.Exercises
where exercise.exerciseDate.Value.Month == selectedMonth && exercise.exerciseDate.Value.Year == selectedYear
select new
{
exercise.exerciseDate,
exercise.duration,
exercise.caloriesBurned,
exercise.averageHR,
exercise.distanceInMiles,
exercise.notes
};
GridView1.DataBind();
}

Answer 1

you have verify the binding of your control grid, i suggest add only object to the datasource of the grid on the pageLoad when the postback its false like this:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
GridView1.DataSource =
from exercise in context.Exercises
where exercise.exerciseDate.Value.Month == selectedMonth && exercise.exerciseDate.Value.Year == selectedYear
select new
{
exercise.exerciseDate,
exercise.duration,
exercise.caloriesBurned,
exercise.averageHR,
exercise.distanceInMiles,
exercise.notes
};
}
GridView1.DataBind();
}
the problem is when you add the objects to datasource , when any event refresh the web page like select the control is unbinding, i hope help you,, see you!!