SQL Server stored procedure Nullable parameter - sql-server

Question

Problem:
When values are provided to the following script then executed using a setup in C# like below (or in SQL Server environment) the values do not update in the database.
Stored procedure:
-- Updates the Value of any type of PropertyValue
-- (Type meaining simple Value, UnitValue, or DropDown)
CREATE PROCEDURE [dbo].[usp_UpdatePropertyValue]
#PropertyValueID int,
#Value varchar(max) = NULL,
#UnitValue float = NULL,
#UnitOfMeasureID int = NULL,
#DropDownOptionID int = NULL
AS
BEGIN
-- If the Property has a #Value, Update it.
IF #Value IS NOT NULL
BEGIN
UPDATE [dbo].[PropertyValue]
SET
Value = #Value
WHERE
[dbo].[PropertyValue].[ID] = #PropertyValueID
END
-- Else check if it has a #UnitValue & UnitOfMeasureID
ELSE IF #UnitValue IS NOT NULL AND #UnitOfMeasureID IS NOT NULL
BEGIN
UPDATE [dbo].[UnitValue]
SET
UnitValue = #UnitValue,
UnitOfMeasureID = #UnitOfMeasureID
WHERE
[dbo].[UnitValue].[PropertyValueID] = #PropertyValueID
END
-- Else check if it has just a #UnitValue
ELSE IF #UnitValue IS NOT NULL AND #UnitOfMeasureID IS NULL
BEGIN
UPDATE [dbo].[UnitValue]
SET
UnitValue = #UnitValue
WHERE
[dbo].[UnitValue].[PropertyValueID] = #PropertyValueID
END
-- Else check if it has a #DropDownSelection to update.
ELSE IF #DropDownOptionID IS NULL
BEGIN
UPDATE [dbo].[DropDownSelection]
SET
SelectedOptionID = #DropDownOptionID
WHERE
[dbo].[DropDownSelection].[PropertyValueID] = #PropertyValueID
END
END
When I do an execution of this script, like below, it does not update any values.
Example execution:
String QueryString = "EXEC [dbo].[usp_UpdatePropertyValue] #PropertyValueID, #Value, #UnitValue, #UnitOfMeasureID, #DropDownOptionID";
SqlCommand Cmd = new SqlCommand(QueryString, this._DbConn);
Cmd.Parameters.Add(new SqlParameter("#PropertyValueID", System.Data.SqlDbType.Int));
Cmd.Parameters.Add(new SqlParameter("#Value", System.Data.SqlDbType.Int));
Cmd.Parameters.Add(new SqlParameter("#UnitValue", System.Data.SqlDbType.Int));
Cmd.Parameters.Add(new SqlParameter("#UnitOfMeasureID", System.Data.SqlDbType.Int));
Cmd.Parameters.Add(new SqlParameter("#DropDownOptionID", System.Data.SqlDbType.Int));
Cmd.Parameters["#PropertyValueID"].Value = Property.Value.ID; // 1
Cmd.Parameters["#Value"].IsNullable = true;
Cmd.Parameters["#Value"].Value = DBNull.Value;
Cmd.Parameters["#UnitValue"].IsNullable = true;
Cmd.Parameters["#UnitValue"].Value = DBNull.Value;
Cmd.Parameters["#UnitOfMeasureID"].IsNullable = true;
Cmd.Parameters["#UnitOfMeasureID"].Value = DBNull.Value;
Cmd.Parameters["#DropDownOptionID"].IsNullable = true;
Cmd.Parameters["#DropDownOptionID"].Value = 2; // Current Value in DB: 3
Details:
After running an execute (via C# code or SQL Server environment) it does not update dbo.DropDownSelection.SelectedOptionID. I'm guessing that it might be because dbo.DropDownSelection.SelectedOptionID is non-nullable and the parameter I'm using to set it is nullable (despite that when setting it shouldn't ever be null). Upon execution the return value is 0. If I run one of the Updates outside of the procedure they work perfectly, hence my suspicion that it has to do with null-able types.
Question(s):
Could this be because the parameters to the stored procedure are nullable and the fields I'm setting aren't?
If not, what could it be?

Answer 1

It looks like you're passing in Null for every argument except for PropertyValueID and DropDownOptionID, right? I don't think any of your IF statements will fire if only these two values are not-null. In short, I think you have a logic error.
Other than that, I would suggest two things...
First, instead of testing for NULL, use this kind syntax on your if statements (it's safer)...
ELSE IF ISNULL(#UnitValue, 0) != 0 AND ISNULL(#UnitOfMeasureID, 0) = 0
Second, add a meaningful PRINT statement before each UPDATE. That way, when you run the sproc in MSSQL, you can look at the messages and see how far it's actually getting.

Answer 2

You can/should set your parameter to value to DBNull.Value;
if (variable == "")
{
cmd.Parameters.Add("#Param", SqlDbType.VarChar, 500).Value = DBNull.Value;
}
else
{
cmd.Parameters.Add("#Param", SqlDbType.VarChar, 500).Value = variable;
}
Or you can leave your server side set to null and not pass the param at all.