LINQ to Entities - how to get column value in a combobox selection

Samio

As displaying LastName in comboBox1, I need to display FirstName in TextBox1.

How can I do that in LINQ ?

My code is as follows

            using (LINQtoEntitiesEntities MyEntities = new LINQtoEntitiesEntities())
            {
                ObjectQuery Emp = MyEntities.Employee;
                comboBox1.DataSource = (from u in Emp select new { u.ID, u.LastName, u.FirstName }).ToList();
                comboBox1.ValueMember = "ID";
                comboBox1.DisplayMember = "LastName";
             }

4 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes14y ago
Accepted answer
I'd create a Dictionary at form level:

private Dictionary dict = new Dictionary();

and populate it when the combobox's data source is being set:

using (LINQtoEntitiesEntities MyEntities = new LINQtoEntitiesEntities())
{
ObjectQuery Emp = MyEntities.Employee;
var list = (from u in Emp select new { u.ID, u.LastName, u.FirstName }).ToList();
foreach(var rec in list) dict.Add(rec.ID, rec.FirstName);
comboBox1.DataSource = list;
comboBox1.ValueMember = "ID";
comboBox1.DisplayMember = "LastName";
}

In the combobox's SelectedIndexChanged eventhandler, you can then do:

int ID = Convert.ToInt32(comboBox1.SelectedValue.ToString());
textBox1.Text = dict[ID];
+1
Samio14y ago
if (comboBox1.SelectedIndex == 0) return;
int ID = Convert.ToInt32(comboBox1.SelectedValue.ToString());
Text1.Text = dict[ID];

Thank you very much Vulpes.
0
Vulpes14y ago
That's what should be happening as I'm using u.ID as the key and u.FirstName as the value of the dictionary.

So, when the selected value (ID) changes in the combobox, the code should write the corresponding FirstName to the textbox.

The LastName should, of course, be displayed in the combobox itself.
0
Samio14y ago
Please, how can I use more than 2 fields with the dictionary ?

because I need to display "u.FirstName" in the textBox1

Thank you
0