Clone the value of a DATETIME column using arrays? - sql-server

Question

I wrote the function below to get the values of two columns in a database, one is composed by integers (ID) and other dates/times in DATETIME format, in SQL Server 2008 R2. It stores the two values in two distinct arrays (lists), defined here:
Dim arrPartIDs As New List(Of Integer)
Dim arrPartUMDates As New List(Of Date)
My goal is to clone the datetime value of each row to the column 'Part_Previous_UMDate', which are currently set as NULL.
However, when my code execute the line:
WinToolSQLCmd.ExecuteReader()
After
WinToolSQLCmd = New SqlCommand("UPDATE WTData.dbo.Parts SET Part_Previous_UMDate = '" & arrPartUMDates.Item(intUMDateCounter) & "' WHERE ID = " & PartID.ToString, WinToolConnection)
The application returns an exception
The conversion of a varchar data type to a datetime data type resulted in an out-of-range value.
I thought that by creating the array (list) arrPartUMDates as a list of date I could simply transfer its values back to the database, but apparently they are created as strings when added to the array...
What's the best approach to clone the DATETIME value in UMDate to Part_Previous_UMDate with full precision? I need to have full precision because later I´ll compare the values of the two columns in order to determine if they need an update.
Any ideas? I've searched for this error message but could not find anything related to dealing with dates in arrays...
Image of table here: http://i.stack.imgur.com/BYT1j.png
Code:
Function MirrorUMDateInPartsTable()
Dim arrPartIDs As New List(Of Integer)
Dim arrPartUMDates As New List(Of Date)
Dim WinToolConnection As New SqlConnection(StrGlobalWinToolConnection)
Dim intUMDateCounter As Integer = 0
WinToolSQLCmd = New SqlCommand("SELECT TOP 5 ID, UMDate FROM WTData.dbo.Parts WHERE WTData.dbo.Parts.Part_Previous_UMDate IS NULL ORDER BY ID", WinToolConnection)
WinToolConnection.Open()
Dim reader = WinToolSQLCmd.ExecuteReader()
While reader.Read()
arrPartIDs.Add(reader.Item(0))
arrPartUMDates.Add(reader.Item(1))
End While
reader.Close()
WinToolSQLCmd.Dispose()
If arrPartIDs.Count > 0 Then
For Each PartID As Integer In arrPartIDs
WinToolSQLCmd = New SqlCommand("UPDATE WTData.dbo.Parts SET Part_Previous_UMDate = '" & arrPartUMDates.Item(intUMDateCounter) & "' WHERE ID = " & PartID.ToString, WinToolConnection)
WinToolSQLCmd.ExecuteReader()
Next
End If
Return Nothing
End Function

Answer 1

You should use SqlParameter to add values to your query (and also to guard against SQL injection). Your problem is that you convert the date to a string in the code and SQL Server treats it as a string. The error about conversion from varchar occurs because the date format is not the one SQL Server uses. If you use parameters, it knows that you pass the date value and sends it correctly - you don't need to worry about any string conversions.
WinToolSQLCmd = New SqlCommand("UPDATE WTData.dbo.Parts SET Part_Previous_UMDate = #DateParam WHERE ID = #IdParam", WinToolConnection)
WinToolSQLCmd.Parameters.Add("#DateParam", arrPartUMDates.Item(intUMDateCounter))
WinToolSQLCmd.Parameters.Add("#IdParam", PartID)
Also, it's an update query, so you should use ExecuteNonQuery to execute your query:
WinToolSQLCmd.ExecuteNonQuery()
ExecuteReader is used when you want to read the data from the database.