How do I prevent duplicate values in a dropdownlist while populating the control from database with value member and data member?

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private void rightsload()
{
DataSet EmpDs = new DataSet();
EmpDs = (DataSet)Session["EmpId"];
DataRow dr = EmpDs.Tables[0].NewRow();
dr["EmpName"] = "All";
dr["EmpId"] = 0;
EmpDs.Tables[0].Rows.InsertAt(dr, 0);

if (EmpDs.Tables[0].Rows.Count > 0)
{

DataView view = new DataView(EmpDs.Tables[0], null, "EmpId", DataViewRowState.CurrentRows);
ddlEmp.DataTextField = "EmpName";
ddlEmp.DataValueField = "EmpId";
ddlEmp.DataSource = view;
ddlEmp.DataBind();
}
}

The "All" multiplies during each postback and thus leads to postback of page too

Posted 13-Jan-15 19:03pm

Member 10239017

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Santosh K. Tripathi · Answer 1 · 2015-01-13T19:15:00

EmpDs = (DataSet)Session["EmpId"];

is showing you have Dataset in session.

when you are saving data in Session["EmpId"] at that time you are running SQL Query in data base.
use DISTINCT Key word in your SQL Query.

Like
SELECT DISTINCT EmpId FROM Your_EMP_TABLE

FOR 2nd Problem

write this code block in IsPostBack check Like

if(!IsPostBack){
DataRow dr = EmpDs.Tables[0].NewRow();
dr["EmpName"] = "All";
dr["EmpId"] = 0;
EmpDs.Tables[0].Rows.InsertAt(dr, 0);

}

I would suggest call rightsload() in IsPostBack check
becouse you need run this method only once when page loads 1st time, not at every postback.

Like

if(!IsPostBack)
{
rightsload();
}