The Web application at could not found. Verify that you have typed the URL correctly. If the URL should be serving existing content, the system administrator may need to add a new request URL mapping to the intended application.

Error:

The Web application at could not found. Verify that you have typed the URL correctly. If the URL should be serving existing content, the system administrator may need to add a new request URL mapping to the intended application.

Solution:

change the visual studio solution to 64 bit in properties as per the below screenshot.

Thats it...

Error: The type or namespace name 'SPSite' could not be found (are you missing a using directive or an assembly reference?)

Error:

The type or namespace name 'SPSite' could not be found (are you missing a using directive or an assembly reference?)

Reason:

Sometimes you will get this issue, while you are testing/developing your SharePoint code through console applications.

By default, visual studio 2010 will set target framework as ".Net Framework 4 Client Profile"

Solution:
We need to change the target framework as ".Net Framework 3.5"

To do this,

1. Go to Solution property in visual studio.

2. Change the target framework to ".Net Framework 3.5" as below:

3. Save all & build the solution.

Thats it...