Why DropDownList SelectedValue not working inside SelectedIndexChanged Event?

Debugger Inside DropDown SelectedIndexChanged Event

Debugger Inside DropDown SelectedIndexChanged Event


In this Blog, we will explore one interesting Bug, which ASP.NET Developers encounter sometimes.

Bug

DropDownList SelectedValue inside SelectedIndexChanged Event does not give the current Selected Value, rather it gives the Default Value or first Option Value.

Walk Through

  1. Let’s declare a DropDownList first.
    <asp:DropDownList ID="ddlDropDownId" runat="server" AutoPostBack="true" 
                      OnSelectedIndexChanged="ddlDropDownId_SelectedIndexChanged">
    </asp:DropDownList>
    
  2. Now to bind the DropDownList, we will write one function like below…
    private void BindDropDownList()
    {
        // Declare a Dictionary to hold all the Options with Value and Text.
        Dictionary<string, string> options = new Dictionary<string, string>();
        options.Add("-1", "Select Option");
        options.Add("1", "Option 1");
        options.Add("2", "Option 2");
        options.Add("3", "Option 3");
        options.Add("4", "Option 4");
        options.Add("5", "Option 5");
    
        // Bind the Dictionary to the DropDownList.
        ddlDropDownId.DataSource = options;
        ddlDropDownId.DataTextField = "value";
        ddlDropDownId.DataValueField = "key";
        ddlDropDownId.DataBind();
    }
    
  3. So, when you run the Page, it would show you the DropDownList on the Page with the Options defined.
    DropDownList on Browser

    DropDownList on Browser

  4. When you select an Option from the DropDownList, it hits the SelectedIndexChanged Event in the Code Behind. If you need to get the SelectedValue, then you will write…
    protected void ddlDropDownId_SelectedIndexChanged(object sender, EventArgs e)
    {
        string value = ddlDropDownId.SelectedValue;
    }
    
  5. Now Here Comes the Main Issue

    When we put a debugger inside the Event and checked, irrespective of the selection of any Option, it always gives you the first Option Value that is “-1”. Refer the debugging Screen Shot at the Top.
    And there is no doubt on the first Option value “-1”, as we can clearly see from the Source HTML of the DropDownList. See highlighted Option in the image below.

    DropDownList Source HTML

    DropDownList Source HTML

    Any Hint Here?

    As we are getting the default value or the first value always, so the guess is that, something is causing the DropDownList to bind again when we select an Option.

    Let’s Find Out !!!

    In the Walk Through Steps, I said about the function BindDropDownList(), which binds the DropDownList. But we need to check where exactly it is getting called. As the DropDownList shows when the Page is Loaded, so it must be present inside the Page Load Event.

    protected void Page_Load(object sender, EventArgs e)
    {
        BindDropDownList();
    }
    

    Now, according to the Event Life Cycle rules, when you select an Option from DropDownList, it Posts Back and goes to Page Load Event first and then it comes to the SelectedIndexChanged Event.
    That means, it comes to the Page Load again on selection of any Option and calls the BindDropDownList(). Thus, the DropDownList is bounded again, before it goes to the SelectedIndexChanged Event. As the DropDownList is bound again, so the SelectedValue is now the first Option Value, which is “-1” (for “Select Option”).

    Fix?

    You might have got the answer. That is IsPostBack Property.

    Gets a value that indicates whether the page is being rendered for the first time or is being loaded in response to a postback.

    It tells you whether you are loading the Page for first time or is it a Post Back due to any Event. Modified code would look something like below.

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            BindDropDownList();
        }
    }
    

    So, Be Careful and Share This to Save Someone’s Day !!!

    You might have played with all the codes in your Page to find out the issue, but at last you come to know that it was because you forgot to check IsPostBack Property. So, Like and Share this with your friends, so that anybody who is unable to find the problem, finally let out a sigh.

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Change Background Color of Ajax HtmlEditorExtender using ColorPickerExtender

[Demo] Change Background Color of HtmlEditorExtender

[Demo] Change Background Color of HtmlEditorExtender


In this Blog, we will learn to change the Background Color of Ajax HtmlEditorExtender using ColorPickerExtender.

Background

There was an question, which eventually gave birth to this Blog.

Here comes the Logic

We have already discussed the Logic in one of the previous Blog Set Content inside AJAX HTMLEditor and EditorExtender using JavaScript. We just need to find out the Edit Panel, that is the div, which is actually showing data for HtmlEditorExtender. Then we can easily assign Selected Color of ColorPickerExtender to that div.

<div contenteditable="true"
     id="txtEditorDemo$HtmlEditorExtenderBehavior_ExtenderContentEditable"
     style="height: 80%; overflow: auto; clear: both;"
     class="ajax__html_editor_extender_texteditor">
</div>

Okay ! Let’s get our feet wet

Get the ColorPickerExtender Selected Color

We can easily get the Selected color by handling the OnClientColorSelectionChanged Event of ColorPickerExtender. We can call a JavaScript function on this Event. Let’s see the markup.

<asp:ColorPickerExtender runat="server" 
                         TargetControlID="txtSelectColor"
                         SampleControlID="sampleBodyColor"
                         PopupButtonID="txtSelectColor" 
                         OnClientColorSelectionChanged="colorChanged">
</asp:ColorPickerExtender>

So, the JavaScript function is colorChanged(). Following code would alert you the Selected Color.

function colorChanged(sender) {
    alert(sender.get_selectedColor());
}
Selected Color on Alert Box

Selected Color on Alert Box

Now, let’s get the HtmlEditorExtender and change its Background Color

There are two ways to do this.

  • Using Sys.Application $find Method

    First find the HTMLEditorExtenderusing ID, then assign the Selected Color to the Background Color Property of its EditableDiv.

    var htmlEditorExtender = $find("<%= heeEditorDemo.ClientID %>");
    htmlEditorExtender._editableDiv
                      .style
                      .backgroundColor = '#' + sender.get_selectedColor();
    
  • Using jQuery Class Selector

    Get the HTMLEditorExtender by its class name ajax__html_editor_extender_texteditor. Then set its Background Color by .css() Method.

    var htmlEditorExtender = $('.ajax__html_editor_extender_texteditor');
    htmlEditorExtender.css('background-color', '#' + sender.get_selectedColor());
    

NOTE

Here we have appended ‘#’ before the Selected Color. That is because Selected Color is only a Hex Number without the prefix ‘#’, as we can see on the screenshot above, where we have alerted the Selected Color.

Thanks !!!

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