Set a default value for my dropdownlist which is filled from database

Question

I'm filling my dropdownlist from database but I want to add "select an item please" to the dropdown along with others and make it default selected item :
I tried to setwriterddl.SelectedValue = "please...";but a runtime error says:

'writerddl' has a SelectedValue which is invalid because it does not exist in the list of items. Parameter name: value

and here is my code:

protected void Page_Load(object sender, EventArgs e)
{
writerddl.SelectedValue = "please...";
if (!IsPostBack)
  {
   writerddl.DataSource = DS.show_all_writers();
   writerddl.DataValueField = "writerid";
   writerddl.DataTextField = "writersname";            
   writerddl.DataBind();
  }
}

Possible duplicate of http://stackoverflow.com/questions/267064/asp-net-add-blank-item-at-top-of-dropdownlist — crthompson, Dec 24 '13 at 05:55

score 4 · Accepted Answer · answered Dec 24 '13 at 05:52

4

Try this code.

protected void Page_Load(object sender, EventArgs e)
{       
   if (!IsPostBack)
   {
       writerddl.DataSource = DS.show_all_writers();
       writerddl.DataValueField = "writerid";
       writerddl.DataTextField = "writersname";            
       writerddl.DataBind();
       writerddl.Items.insert(0, new ListItem("Please select",""));
   }
}

answered Dec 24 '13 at 05:52

Raghubar

2,768
1
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31

aha okay I'll try this – Aya Mohammad Dec 24 '13 at 05:57
1

This is the correct way. Also note, the 0 at the beginning is the index as to where to insert the item. If you are dealing with this dropdown in jQuery, ensure you handle this insert.. – Subliminal Hash Dec 24 '13 at 06:03
mmm ... okay ... but it doesn't work if I removed the "`if (!isPostback)`" – Aya Mohammad Dec 24 '13 at 06:14
because when page post back happened if there is no if (!isPostback) drop down will reload again and again – Raghubar Dec 24 '13 at 06:16

Samiey Mehdi · Answer 2 · 2013-12-24T06:20:13.570

1

Remove this:

writerddl.SelectedValue = "please...";

and use this:

//....    
writerddl.DataBind();
writerddl.Items.Insert(0, "please...");
//...

Update:

use Clear() method like this:

protected void Page_Load(object sender, EventArgs e)
{  
   writerddl.Items.Clear();
   writerddl.DataSource = DS.show_all_writers();
   writerddl.DataValueField = "writerid";
   writerddl.DataTextField = "writersname";            
   writerddl.DataBind();
   writerddl.Items.Insert(0, "please...");
}

edited Dec 24 '13 at 06:20

answered Dec 24 '13 at 05:51

Samiey Mehdi

9,184
18
49
63

where in the code ? you mean instead of writerddl.SelectedValue = "please..."; ? – Aya Mohammad Dec 24 '13 at 05:52
mmm ... okay ... but it doesn't work if I removed the "`if (!isPostback)`" – Aya Mohammad Dec 24 '13 at 06:15

Naveen · Answer 3 · 2013-12-24T06:53:42.083

-1

Use the below code. Note the selected-value line moved below and that makes difference. Hope the item with Value "please..." exists in the dropdown.

 protected void Page_Load(object sender, EventArgs e)
    {           
        if (!IsPostBack)
        {
            writerddl.DataSource = DS.show_all_writers();
            writerddl.DataValueField = "writerid";
            writerddl.DataTextField = "writersname";
            writerddl.DataBind();
            writerddl.SelectedValue = "please...";
        }

    }

Update : "Hope the item with Value "please..." exists in the dropdown" changing this line to "Hope the item with Value "please..." exists in the binding source".

Update 1: If the source don't have item "please..." here is the below code. protected void Page_Load(object sender, EventArgs e) {

    if (!IsPostBack)
    {
        writerddl.Items.Add(new ListItem("Select An Item", "please..."));
        writerddl.DataSource = DS.show_all_writers();
        writerddl.DataValueField = "writerid";
        writerddl.DataTextField = "writersname";
        writerddl.DataBind();
        writerddl.SelectedValue = "please...";
    }

}

edited Dec 24 '13 at 06:53

answered Dec 24 '13 at 05:55

Naveen

1,496
1
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I think the point of the OP's post is that the "please..." does NOT exist in the datasource, but he wants it added. – crthompson Dec 24 '13 at 05:57
@paqogomez Is it possible to select an item before binding?. For the first load the code is trying to select before binding. I am trying to point out that. In comment i also added "hope the item with Value "please..." exists in the dropdown". – Naveen Dec 24 '13 at 05:59
You are correct in pointing that out, but incorrect in delivering a working solution. – crthompson Dec 24 '13 at 06:02
I think you need to write it so that you assume that the value is NOT in the datasource. – crthompson Dec 24 '13 at 06:03

Set a default value for my dropdownlist which is filled from database

3 Answers3