CODEWITHSUNDEEP
javascriptasp.net
Cole W
Cole W

Reputation: 15303

Unable to get property X of undefined or null reference

After upgrading an asp.net web forms application from the 2.0 framework to the 4.0 framework it appears references like the following are broken in javascript

document.RF_Login.hidSubmit.value="Yes";

It results in the following error:

javascript error

Why does this occur when upgrading to the 4.0 framework? Is there something I can do to not have to update all references like this in the entire website?

EDIT

The name of the page is RF_Login.aspx and inside the page the following exists:

<FORM id="RF_Login" method="post" runat="server">

Upvotes: 1

Views: 949

Answers (1)

Seany84
Seany84

Reputation: 5596

I believe the issue is due to .NET 2.0 using AutoID for the .NET control ID generation. Whereas, .NET 4.0+ uses the predictable clientId mode.

As taken from: .NET Framework 4 Migration Issues

The new clientIDMode setting in ASP.NET 4 lets you specify how ASP.NET generates the id attribute for HTML elements. In previous versions of ASP.NET, the default behavior was equivalent to the AutoID setting of clientIDMode. The default setting is now Predictable.

Resolution:

To disable the new client ID mode, add the following setting to the Web.config file:

<pages clientIDMode="AutoID" />

or

<pages controlRenderingCompatibilityVersion="3.5" />

Or both combined:

<pages clientIDMode="AutoID" controlRenderingCompatibilityVersion="3.5" />

Upvotes: 1

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