Stored Procedure Variable (Code error I believe is there) - asp.net

Question

I am trying to create a script to tidy all the columns and rows in SQL Server (I will be doing more than trimming but once it works I can plug into app-code I have already)
I think I am there but it does not seem to update - maybe the stored procedure is wrong? I believe the error is here.. -- I have looked around about variables in stored procedures and think it looks correct to me.
Insert statements for procedure here
UPDATE systemUsers
SET #ColumnName = #Update
WHERE ID = #ID
Full script...
Protected Sub btnTest_Click(sender As Object, e As System.EventArgs) Handles btnTest.Click
'Select the column names
Dim cn As SqlConnection = New SqlConnection()
Dim cmd As SqlCommand = New SqlCommand()
Dim dr As SqlDataReader
Dim i As Integer = 0
cn.ConnectionString = ConfigurationManager.ConnectionStrings("mySQLConnectionString").ConnectionString
cmd.Connection = cn
' this gets the colum name
cmd.CommandText = "select COLUMN_NAME FROM INFORMATION_SCHEMA.Columns where TABLE_NAME = 'systemUsers'"
'Open the connection to the database
cn.Open()
' Execute the sql.
dr = cmd.ExecuteReader()
' Read all of the rows generated by the command (in this case only one row).
CheckBoxList1.Items.Clear() 'remove all items for the new list
Do While dr.Read()
i = i + 1
Session.Item("ColumnName" & i) = dr.Item("COLUMN_NAME").ToString()
Loop
' Close your connection to the DB.
dr.Close()
cn.Close()
Dim j As Integer = 1
For j = 1 to i
cn.ConnectionString = ConfigurationManager.ConnectionStrings("mySQLConnectionString").ConnectionString
cmd.Connection = cn
cmd.CommandText = "Select * From [systemUsers]"
'Open the connection to the database
cn.Open()
' Execute the sql.
dr = cmd.ExecuteReader()
' Read all of the rows generated by the cmd (in this case only one row).
Dim vName As String = ""
If vName = "ID" Then
'skip as ID should never be edited!!
Else
Do While dr.Read()
vName = Session.Item("ColumnName" & j).ToString ' put into vName for Stored Procedure
Dim sConnString As String = System.Web.Configuration.WebConfigurationManager.ConnectionStrings("mySQLConnectionString").ConnectionString
Dim dsNames As SqlDataSource
dsNames = New SqlDataSource
dsNames.ConnectionString = sConnString
Dim sSQL As String
sSQL = "SPTidy"
dsNames.UpdateCommand = sSQL
dsNames.UpdateCommandType = SqlDataSourceCommandType.StoredProcedure
dsNames.UpdateParameters.Clear()
dsNames.UpdateParameters.Add("ID", dr.Item("ID").ToString())
dsNames.UpdateParameters.Add("Update", Trim(dr.Item(vName).ToString()))
dsNames.UpdateParameters.Add("ColumnName", vName)
dsNames.Update()
dsNames = Nothing
Loop
End If
j = j + 1
' Close your connection to the DB.
dr.Close()
cn.Close()
Next
End Sub
Stored procedure:
create PROCEDURE [dbo].[SPTidy]
#ID bigint,
#Update nvarchar(max),
#ColumnName nvarchar(max)
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
-- Insert statements for procedure here
UPDATE systemUsers
SET #ColumnName = #Update
WHERE ID = #ID
END

Answer 1

That code won't throw an error message because it's simply updating the variable. To have a dynamic column name you need to use dynamic SQL (or complicated case statements) but dynamic SQL is better in this instance.
DECLARE #sql nvarchar(max) = '';
SET #sql = N'UPDATE systemUsers SET ' + #ColumnName + N' = ' + #Update + N' WHERE ID=' + #ID
EXEC sp_executesql #sql
Hope this helps :)