"Object expected" error while calling javascript function

Question

I want to change the visibility of a textbox, according to the value selected in a dropdownlist.

I have created the function like this:

function ShowGiftCardSource() {
        var ddlGiftCardSource = document.getElementById('<%=ddlGiftCardSource.ClientID%>');
        var txtGiftCardSource = document.getElementById('<%=txtGiftCardSource.ClientID%>');

        if (ddlGiftCardSource.value == "Other") {
            txtGiftCardSource.style.visibility = "visible";
            txtGiftCardSource.focus();
        }
    }

In the CS Page:

ddlGiftCardSource.Attributes.Add("onChange", "OnSelectedIndexChanged();");

and in the control:

<asp:DropDownList ID="ddlGiftCardSource" runat="server" Width="151px" onChange="ShowGiftCardSource();">

But I'm getting the following error:

Microsoft JScript runtime error: Object expected

Could some one please help me to resolve it?

score 1 · Accepted Answer · 2011-02-23 14:56:00Z

1

Change the code behind to:

ddlGiftCardSource.Attributes.Add("onChange", "ShowGiftCardSource();");

And remove the onchange from the tag:

<asp:DropDownList ID="ddlGiftCardOccasion" runat="server" Width="151px">

The onchange in the tag is the server side method to call.

Edit: in case you already have server side method you must first add AutoPostBack to the drop down then in the server side onchange event show the textbox:

<asp:DropDownList ID="ddlGiftCardOccasion" runat="server" Width="151px" OnChange="ShowGiftCardSource" AutoPostBack="True">

And in your C# code behind:

void ShowGiftCardSource(object sender, EventArgs e) {
  //code.....
  txtGiftCardSource.Visible = true;
}

And of course, get rid of the ddlGiftCardSource.Attributes.Add line.

edited Feb 23, 2011 at 14:56

answered Feb 23, 2011 at 14:27

user447356

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4 Comments

NaveenBhat Over a year ago

onChange event of the ddlGiftCardSource.

user447356 Over a year ago

@Knv You can't have both the client side event and server side event, it's meaningless. See my edit.

NaveenBhat Over a year ago

In the server side, there is no events of it. I told about the 'onChange', which is registered while loading the page. Actually, I have put a breakpoint on 'ShowGiftCardSource()'[JavaScript] method and executed it but nothing happened, when I selected a item from the dropdown. I'm not getting, why this is happening?, if you know any alternatives please suggest me. Thank you for your response.

user447356 Over a year ago

Sorry I completely lost you. I provided you with all the options, can't really explain any better.

EvgK · Accepted Answer · 2011-02-23 14:26:21Z

1

Maybe thats because you are using ShowGiftCardOccasion() method in onChange handler, but you method name is ShowGiftCardSource() ? Then javascript just cannot find method with correct name.

answered Feb 23, 2011 at 14:26

EvgK

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1 Comment

NaveenBhat Over a year ago

<asp:DropDownList ID="ddlGiftCardSource" runat="server" Width="151px" onChange="ShowGiftCardSource();">

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