Javascript for dropdown

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Hi Friends ....

I need to write Javascript for dropdown list .

For selected value not equal to 'Select'

ASP.NET

<asp:DropDownList ID="dropstatus" runat="server" CssClass="dropdown">
                            <asp:ListItem Text="Select"></asp:ListItem>
                            <asp:ListItem Text="Open"></asp:ListItem>
                            <asp:ListItem Text="Fixed"></asp:ListItem>
                            <asp:ListItem Text="Processing"></asp:ListItem>
                        </asp:DropDownList>

C#

script type="text/javascript">
    function validate() {

        if (document.getElementById('<%=txtcomp.ClientID%>').value == "") {
            alert("Name Feild can not be blank");
            document.getElementById("<%=txtcomp.ClientID%>").focus();
            return false;

        }

        var txt = document.getElementById('<%=dropstatus.ClientID %>')
        if ((txt.options[txt.selectedIndex].text) == "Select") {
            alert("Password Feild can not be blank");
            document.getElementById("<%=dropstatus.ClientID%>").focus();
            return false;

        }

    }

    </script>

The Above code is correct or Wrong.

Please help me

Posted 30-May-12 0:47am

Arul R Ece

Updated 30-May-12 2:00am

v3

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Comments

Rahul Rajat Singh 30-May-12 6:55am

looks fine to me. are you getting any problem?

Arul R Ece 30-May-12 7:00am

I am getting the below error.
The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>).

member60 30-May-12 7:19am

see my edited answer

Arul R Ece 30-May-12 7:59am

Till get same error

3 solutions

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Rajesh Kariyavula · Answer 1 · 2012-05-30T01:42:00

You can register the control in your code behind as mentioned below:

C#

Page.RegisterHiddenField("hdnDropDownList", dropstatus.ClientID);

And use it in your Javascript Code:

JavaScript

var _dropDown = document.getElementById('hdnDropDownList').value;
if (document.getElementById(_dropDown).selectedIndex =="Select") {
    alert("Please select City");
    document.getElementById(_dropDown).focus();
    return false;
}

member60 · Answer 2 · 2012-05-30T01:11:00

the code you are posted works well . The problem could occur when you use Value proerty in ListItem , such as :

ASP.NET

<asp:listitem value="0" text="Select" xmlns:asp="#unknown"></asp:listitem>

then you can have Text by :

JavaScript

var txt=document.getElementById('<%=dropstatus.ClientID %>')
if((txt.options[txt.selectedIndex].text)=="Select")
//further code

or

C#

if((txt.options[txt.selectedIndex].value)=="Select")
//further code

To fix the error you described in comments follow:
1.Remove the part which has server tags and place it somewhere else if you want to add dynamic controls from code behind. You can add this javascript code to the html body it will solve your problem.

2. You can use <%# instead of <%=

This changes the code block from a Response.Write code block to a databinding expression. Since <%# … % > databinding expressions aren’t code blocks, the CLR won’t complain.

aarohi verma · Answer 3 · 2012-05-30T00:56:00

Solution 2

C#

if (document.getElementById("<%=dropstatus.ClientID %>").selectedIndex =="Select") {
            alert("Please select City");
document.getElementById("<%=dropstatus.ClientID%>").focus();
            return false;
        }

try this.

put SelectedIndex instead of value.

if this help you than accept solution so other can view this.

Posted 30-May-12 0:56am

aarohi verma

Comments

Arul R Ece 30-May-12 7:09am

Hi Friend,...
I am getting the below error.
The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>). Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Web.HttpException: The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>). Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [HttpException (0x80004005): The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>).] System.Web.UI.ControlCollection.Add(Control child) +8680983 AjaxControlToolkit.ScriptObjectBuilder.RegisterCssReferences(Control control) in C:\Users\wahlind\Desktop\Code\ControlToolkit\AjaxControlToolkit\ExtenderBase\ScriptObjectBuilder.cs:249 AjaxControlToolkit.ExtenderControlBase.OnPreRender(EventArgs e) in C:\Users\wahlind\Desktop\Code\ControlToolkit\AjaxControlToolkit\ExtenderBase\ExtenderControlBase.cs:352 System.Web.UI.Control.PreRenderRecursiveInternal() +80 System.Web.UI.Control.PreRenderRecursiveInternal() +171 System.Web.UI.Control.PreRenderRecursiveInternal() +171 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +842

member60 30-May-12 7:22am

have a look at my edited answer.

markovl 30-May-12 7:18am

This is just wrong. The selectedIndex property of the select object is a number, it's not a string, so this condition will always evaluate to false.

Javascript for dropdown

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