The reason for this error is i have include more than one (my case is two) ScriptManager in the same page. In my case in master page and in another page (login.aspx) that include master page.
To solve it, simple remove the ScriptManager in login.aspx. Problem solved.
3 comments:
Hello. I have the same problem and I came across your blog.
I`m using user controls inside user controls. so I cant remove any of the scripmanagers control...
The only solution that I got was to remove all scriptmanagers and add only one to the MastePage.
Problem solve!
Chears.
Opulently I agree but I about the post should prepare more info then it has.
Thanx Bro Your Post really help me
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