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Hi Jason,

This is usually caused by the files in /Admin being out of sync with those in /bin. Did you update everything or just the files in the bin folder?

Imar

Hi Jason and Imar,

The method was changed from GetReservedAmount(string productId, string variantId) to GetReservedAmount(string productId, string variantId, long stockLocationId, string unitId), so product reservation accounts for stock location and units.

Mario

As Imar explained this is issue on upgrade process, seems you need to double check Dynamicweb.ecomerce DLL that match with 9.13.8 version.

most of the time this happen when you use VS and references are not updated correctly, and when you build it try to bring old versions 

I believe what Mario mentioned was the actual issue we found

Then i have doubt with your error message 

System.MissingMethodException: Method not found

if method available with different parameters, Error message is different in either debug envirnment or running envirnment.

if i ask where you get this error ?

This error was showing the product detail pages and we few other places when the add to cart was trying to be used. 

Bump 

This is a real problem. We have worked around it, but a normal principle is that method signatures shouldn't change with hotfix upgrades. We would like to trust that we can upgrade within a hotfix version and the chance of something breaking is as close to zero as possible.

This method signature change occurred between 9.13.7 and 9.13.8 (if I remember correctly, since it was a few weeks ago when it first came up).

Would it be possible to add an overload to make this backwards compatible? Otherwise, we need to remember to use an updated DLL on each upgrade that crosses that hotfix version, and possibly other sites with customzations will break on that upgrade. 

Scott