Run sharepoint code in asp.net application

Question

In asp.net application , I wrote c# code to add item in sharepoint list and I got error

Microsoft SharePoint is not supported in 32-bit process

I set the platform to 64x with no avail !!!

Answer 1

In project Properties, try to change IIS Express to Local IIS as the following:

• Open Visual Studio as administrator.
• Right click on your project > properties.
• Don't change the platform and platform target, just set it as default any CPU
• At web section > below servers > select Local IIS > Click on create virtual directory.
• Save and run the application that should be working.

Answer 2

The server must be in 64b where you run your application, not only the configuration of platforme in VisualStudio settings.

Is your application asp.net run on the SharePoint serveur (front-end, applicative ...)?
If yes, you can use the SharePoint API Server site (in the microsoft.SharePoint.dll).
Else you should (and I recommend this) to use the CSOM (Client SharePoint Object Model).

You can find a lot of doc on internet. Like :
How to: Create, Update, and Delete List Items
SharePoint Client Object Modal (CSOM)