I am trying to use Ajax control toolkit in asp.net website. I copied the dll from one of my previous sample project. It has the following details
Assembly Version – 3.5.40412.0
File Version - 3.5.40412.2
Internal Name: Ajax Control Toolkit
Language : Neutral
Product Version - 3.5.40412.2
When I add reference to this assembly, it appears as “AjaxControlToolkit-3.5.40412.2” in the reference list. When I run the solution, I get a FileLoadException:
Could not load file or assembly 'AjaxControlToolkit-3.5.40412.2' or one of its dependencies.
The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
I think the problem is with the difference in Assembly version and File version. Is it so? How can we overcome it?
Edit the web.config file to remove the reference, which is not required for normal operation:
1 - Open the web.config file in the root of your site
2 - Find the following line and comment it out():xxxxx-is your assembly name.
<add assembly="xxxxx", Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
3 - Save and close the web.config file and try again
来源：https://stackoverflow.com/questions/10295614/mismatch-in-assembly-and-product-version