从C＃中的背后代码调用javascript函数时，document.getElementById（）无法正常工作

Question

I have a javascript function that is working fine in default.aspx when click on a link button. However, when I call this function from code behind, it cant work.

Here is part of my code in default.aspx :

function loadAdditionalInfoDialog(qtyId)
{
    alert(qtyId);
    var qty = document.getElementById(qtyId).value;
    alert(qty);
}

Here is part of my code in code behind (default.aspx.cs) when click on a button:

protected void btnRedeemAll_Click(object sender, EventArgs e){
    TextBox txtQty = (TextBox)itm.FindControl("txtQty");

    ScriptManager.RegisterStartupScript(this.Page, this.GetType(), "temp", "<script>loadAdditionalInfoDialog(" + txtQty.ClientID + ")</script>", false);
}

The alert(qtyId) is working for both side and print out the same word. (default page and code behind). But code behind fail to alert(qty). Anyone know what is my problem?

Noted that the qtyId is a text box id inside a repeater in default.aspx.

Answer 1

probably you are passing the wrong ClientID .

Use a java-script debugger (such as FireBug) and check if var qty = document.getElementById(qtyId); is not null (it will probably be).

Have also a look here

Answer 2

Could you try below?

protected void btnRedeemAll_Click(object sender, EventArgs e){
ScriptManager.RegisterStartupScript(this.Page, this.GetType(), "temp", "  <script>loadAdditionalInfoDialog('" + txtQty.ClientID + "')</script>", false);
}

It seems you're missing single quotes around clientid being passed.

Answer 3

Are you missing the quotes in the argument '" + txtQty.ClientID + "'

protected void btnRedeemAll_Click(object sender, EventArgs e){
    ScriptManager.RegisterStartupScript(this.Page, this.GetType(), "temp"," <script>loadAdditionalInfoDialog('" + txtQty.ClientID + "')</script>", false);

}

Answer 4

Try that:

Page.ClientScript.RegisterStartupScript(this.GetType(), "temp", "<script>loadAdditionalInfoDialog('" + txtQty.ClientID + "')</script>", false);

This is method for scripts that should be bound during initial page rendering.

Answer 5

My guess is the problem is caused by that you're creating the control txtQty on the button click event handler.

This is a dynamically-created control and might not exist in HTML generated by the ASP.NET engine.

Try using a control that is on the page and that you added in design view and check if you get the same issue.

Update: Apologies. In the button click event handler you're trying to find the control. Why are you doing that? Is the control a dynamically-created control created somewhere on another part of the application?