What data type does the SQLCommand method ExecuteScalar() return?

Question

In SQL Server, ID is a not null integer, and an identity.

When I run the following code, I get an InvalidCastException on the last line:

SqlCommand         


        

Answer 1

It's probably returning a boxed instance of a different numeric type, such as long.
A boxed long cannot be converted to int.

You can call GetType() on the return value to see what type it really is.

Answer 2

SCOPE_IDENTITY() returns a decimal in code, otherwise known as NUMERIC(38,0) in TSQL.

http://msdn.microsoft.com/en-us/library/ms190315.aspx

So if you want a direct cast, you can do (int)(decimal)cmd.ExecuteScalar();. Note that a decimal to int conversion can lose information in the strictest sense, so just be advised. But with your identity column being an integer, the conversion will be safe.

Answer 3

From the end of your INSERT statement

SELECT SCOPE_IDENTITY()

It's returning the identity value of the row inserted into the [Users] table.