Dear friend,
First of all if u are beginner in C#.Please download Murach C# 2008 by wrox publication.That may be best for beginner to learn C#.
let go to the point
if your combo box name
cmbEmployee
then
declaire DataTable
DataTable dt=new DataTable();
Here for dt=Query required from database
cmbEmployee.datasource=dt;
if it is Desktop Application then
cmbEmployee.DisplayMember="Column Name";
if it is asp then
cmbEmployee= "EmployeeName";
cmbEmployee.DataValueField = "EmployeeID";
cmbEmployee.DataBind();
Masud