当文本框通过javascript更改客户端时，ASP.NET文本框在回发后丢失值

Question

I am setting the value of a textbox via javascript client-side. When I refresh the page the value is lost.

The textbox is not disabled or set to read-only.

I have read suggestions to put the value in a hidden field, I'd prefer not to do this. It seems like a hack.

The textbox is in a user control as such:

<div id="Row" class="RaidRow" runat="server">
    <asp:Button ID="RaidRowButton" runat="server" CssClass="RaidRowButton" OnClick="RaidRowButton_Click" />
    <asp:TextBox ID="CharacterNameTextBox" runat="server" CssClass="RaidRowControl SlotTextBox" MaxLength="12" />
    <asp:Label ID="ClassNameLabel" runat="server" CssClass="RaidRowControl ClassLabel" />
</div>

This control is on the .aspx page.

When the user double-clicks the textbox, presses enter while the textbox has focus, or changes the text, the following javascript function is called:

function VerifyCharacter(slotNumber, event)
{
    var enterWasPressed = false;

    if (event && event.which == 13)
    {
        enterWasPressed = true;
    }
    else if (window.event && window.event.keyCode == 13)
    {
        enterWasPressed = true;
    }

    if (event == null || enterWasPressed)
    {
        var realmName = 'Lightninghoof';

        var characterNameTextBox = GetCharacterNameTextBox(slotNumber);
        characterNameTextBox.style.color = '#CCCCCC';

        var classLabel = GetClassNameLabel(slotNumber);
        classLabel.style.color = '#CCCCCC';
        classLabel.innerHTML = 'Unknown';

        WoW_Stats.CharacterInformation.GetCharacterInformation(realmName, characterNameTextBox.value, slotNumber, GetCharacterInformation_Success, GetCharacterInformation_Failed);
    }
}

Once the web-service call is complete, the following javascript function is called:

function GetCharacterInformation_Success(characterInformationResult)
{
    var characterInfo = Sys.Serialization.JavaScriptSerializer.deserialize(characterInformationResult, true);

    var classLabel = GetClassNameLabel(characterInfo.SlotNumber);
    classLabel.style.color = characterInfo.ClassColor;
    classLabel.innerHTML = characterInfo.ClassName;

    var characterNameTextBox = GetCharacterNameTextBox(characterInfo.SlotNumber);
    characterNameTextBox.style.color = characterInfo.ClassColor;
}

The only problem is that when I refresh the page, the text in the CharacterNameTextBox and ClassNameLabel, which were set client-side via javascript, are lost.

How can I make sure the controls retain their value between postbacks?

Answer 1

Refreshing the page (pressing F5) is different than a postback. I don't believe the value in your text box is going to be posted back to the server on a refresh. The value in the text box will get posted back to the server on a postback though (as long as the ReadOnly attribute of the TextBox is not set to true, but that's a different story).

Answer 2

I think if the textbox is not editable : Enabled = False or ReadOnly= false.
Asp.net "for security reasones" takes the value from this textbox from its ViewState.
That's why when you use something like a HiddenField or Input, you can get the value.

Answer 3

In the page preinit event, try accessing the value like this:

Request["CharacterNameTextBox"]

I was running into the same issue (a value set via javascript would never post back, but a typed in value would) and a co-worker suggested it. Dead on, works like a charm.

Answer 4

The only problem is that when I refresh the page, the text in the CharacterNameTextBox and ClassNameLabel, which were set client-side via javascript , are lost.

Since you are setting the value client-side I would suggest using cookies to store that data and checking for that cookie in your client-side, since ViewState will not help here if you are just setting the value client-side regardless of what CodeBehind would set it to be.

Answer 5

Another solution is Session, you can assign a session in the first load or from external page, then check if session is not null, then set value to text box. Here is example: in external page:

   if (id == "txtDD")
        {
          Session["DD"] = calendar.SelectedDate.ToShortDateString();
        }
and in code behind check it:

protected void Page_Load(object sender, EventArgs e)
   {
    if(Session["DD"]!= null)
       txtDD.Text =Session["DD"].ToString();
   }

Answer 6

Instead of making a text box readonly you can try this

onKeyPress = "javascript: return false;" onPaste = "javascript: return false;" 

it will not loose its value.

Answer 7

Storing values in a hidden field is no more of a hack than .NET Web Forms itself is. Much of the application data is passed/stored in the hidden __VIEWSTATE field.

That being said, could you clarify what is going on? Are you setting the value on page load, or in reaction to some user action? Could you provide some of your code so that we can have a clearer picture of what you are doing?

EDIT

Are you explicitly setting the value of either of the textbox or the label in your page load/postback codebehind? That would override any values being set by the client script. I can't think of any other reason why the values would not persist. If you're really desperate, you could send the information back to the server via an AJAX call at the end of your javascript function, so that you have it in server memory somewhere.

Answer 8

when do you set the value? You could set the value onload of the page in javascript as long as you are using the clientId of the textbox.

Answer 9

The problem could be one of two things. The refresh could clear then field. Also, if you are posting back, do you set the value of the text box on the page load (or unload) event?

Answer 10

You have to remember, KISS.

Just think of your existing fields as presentational in nature and add hidden input fields with a runat="server" attribute and set those with JavaScript in your same client-side event.

Those are your real values you want in your code-behind methods and you'll be able to grab those no problem. Since the textbox object is a .NET abstraction, I would suggest when doing heaving client-side work using HTML inputs that are run at the server. It seems to save me a headache when I'm knee-deep in web forms BS.

I think there are a lot of solutions here, but I'm all for breaking the wrist and walking away if I can.