Get return value from stored procedure

I found it!
I can read the return value with an output parameter that has to be used in this way:

// define a new output parameter
var returnCode = new SqlParameter();
returnCode.ParameterName = "@ReturnCode";
returnCode.SqlDbType = SqlDbType.Int;
returnCode.Direction = ParameterDirection.Output;

// assign the return code to the new output parameter and pass it to the sp
var data = _context.Database.SqlQuery<Item>("exec @ReturnCode = spItemData @Code, @StatusLog OUT", returnCode, code, outParam);