Procedure with update new information - sql-server

Question

So I have been working on simple procedure for school that asks me to:
(Create a stored procedure called UpdateProduct that takes in a required Product ID parameter and optionally any other one or more fields in the Product table. Then the proc will update any fields passed in but leave any other fields as they were.
If executed like this: UpdateProduct #productID = 1, #name = ‘Steel Ball Bearing’; Only the name should change, all other fields should still contain the value there before the procedure
was called)
This is what I have but still I cant seem to get it to work properly. I am going nuts because I have been trying to figure this out for several days. Any help pointing out my mistake would be awesome.
USE AdventureWorks2012
GO
CREATE PROC UpdateProduct2
#ProductID INT ,
#Name nvarchar (50)= ISNULL,
#ProductNumber nvarchar (25) =ISNULL,
#Color nvarchar (15)=ISNULL
AS
BEGIN
UPDATE [Production].[Product]
SET
Name = ISNULL (#Name,Name),
ProductNumber = ISNULL (#ProductNumber,ProductNumber),
Color = ISNULL (#Color, Color)
WHERE #Name=Name
END

Answer 1

I think your where clause should be:
WHERE ProductID = #ProductID;
rather than
WHERE #Name=Name
Also you need to use NULL rather than ISNULL to set the parameter defaults:
CREATE PROC UpdateProduct2
#ProductID int,
#Name nvarchar(50) = NULL,
#ProductNumber nvarchar(25) = NULL,
#Color nvarchar(15) = NULL
AS
BEGIN
UPDATE [Production].[Product]
SET Name = ISNULL (#Name,Name),
ProductNumber = ISNULL (#ProductNumber,ProductNumber),
Color = ISNULL (#Color, Color)
WHERE ProductID = #ProductID;
END
EDIT
To answer the question about specifying NULL as the default, yes there is a reason, it allows you to call the procedure without passing the parameter.
Take the following two procedures:
CREATE PROCEDURE dbo.P1 #p1 VARCHAR(20), #p2 VARCHAR(20)
AS
BEGIN
SELECT P1 = #p1, P2 = #p2;
END;
GO
CREATE PROCEDURE dbo.P2 #p1 VARCHAR(20) = NULL, #p2 VARCHAR(20) = NULL
AS
BEGIN
SELECT P1 = #p1, P2 = #p2;
END;
The first using no default, and the latter with NULL as the default. The only way to call the first procedure is to send all parameters, e.g.
EXECUTE dbo.p1;
EXECUTE dbo.p1 #P2 = 'TEST';
EXECUTE dbo.p1 #P1 = 'TEST';
Will generate the following errors:
Msg 201, Level 16, State 4, Procedure P1, Line 0
Procedure or function 'P1' expects parameter '#p1', which was not supplied.
Msg 201, Level 16, State 4, Procedure P1, Line 0
Procedure or function 'P1' expects parameter '#p1', which was not supplied.
Msg 201, Level 16, State 4, Procedure P1, Line 0
Procedure or function 'P1' expects parameter '#p2', which was not supplied.
Whereas this:
EXECUTE dbo.p2;
EXECUTE dbo.p2 #P2 = 'TEST';
EXECUTE dbo.p2 #P1 = 'TEST';
Will generate:
P1 P2
NULL NULL
P1 P2
NULL TEST
P1 P2
TEST NULL