CODEWITHSUNDEEP
c#.netasp.net.net-3.5drop-down-menu
Parth Bhatt
Parth Bhatt

Reputation: 19469

C#.Net : Duplication of values in my DropDownlist

I have a dropdownlist ddlTables which contains the table names in my database and I display the table contents in the grid based on the table selected.

I am filling the data into my dropdownlist on Page_Load event using the following code:

ddlTables.Items.Add("-SELECT-");
String getTables = "SELECT TABLE_NAME FROM Information_Schema.Tables where Table_Type = 'BASE TABLE'";
MySqlConnection objMyCon10 = new MySqlConnection(strProvider);
objMyCon10.Open();
MySqlCommand cmd10 = new MySqlCommand(getTables, objMyCon10);
MySqlDataReader r = cmd10.ExecuteReader();
while (r.Read())
{
    ddlTables.Items.Add(r[0].ToString());
}
objMyCon10.Close();

When I click Go button it should display the table contents of the table selected.

But on click of Go button, I have observed that it first calls the Page_Load event first and then calls btnGo_Click.

So it duplicates all the values in my dropdownlist.

Eventually each table name in my dropdownlist list appears twice after I click the Go button.

How to remove this duplication of the values?

Upvotes: 0

Views: 2081

Answers (4)

Khalid
Khalid

Reputation: 645

Sample Program

if(!IsPostBack) 
{ 
    //Creating Items 
    ListItem li1 = new ListItem("Male", "1"); 
    ListItem li2 = new ListItem("Female", "2"); 
    ListItem li3 = new ListItem("Secret", "3"); 
    //Adding Items to DropDownList 
    DropDownList1.Items.Add(li1); 
    DropDownList1.Items.Add(li2); 
    DropDownList1.Items.Add(li3); 
}

Upvotes: 1

Brian Scott
Brian Scott

Reputation: 9361

2 options:

If you only need the items to be kept consistent from the point you first visit the page then use:

if(!Page.IsPostback) { /* bind here */ };

If you need the values to be live on very page refresh then disable the viewstate on the control and no previous values will be reapplied to the dropdownlist on postback.

Upvotes: 0

V4Vendetta
V4Vendetta

Reputation: 38210

Put your code for filling up the items of the dropdown in a

if(!Page.IsPostback)
{[dropdown filling/binding code here]}

conditional check, this will avoid filling up of the values again when you click on the button and also retain the selection if any made by you in the dropdown

Upvotes: 1

Rob Fonseca-Ensor
Rob Fonseca-Ensor

Reputation: 15621

Try putting that code into an

if(!Page.IsPostBack)
{
    //your code
}

block

Upvotes: 2

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