With the current trend of SOI (Service Oriented Architecture), it is very common for Web Application to use Web Service in their back-end. Since the back-end processing is implemented as a Web Service, the Front-End (UI Layer) must convert the data into XML-text before sending it for processing.
This conversion from a data-type to xml text, then back to its original data-type, will introduce a pitfall that will plunge many developers into a runtime error. Learning from my past mistakes, I come up with these points that hopefully will save you from experiencing a runtime error (read, an unpleasant call from your customer explaining the problem):
- Always check your data before conversion. VB.Net has these functions to help you: IsDBNull(), IsNothing(), IsNumeric(). Use them wisely.
- Always initialize a variable before assigning a value.
- Try-Catch is there not for nothing.
To illustrate above points, I’ll make a few examples here:
Bad Code:
Dim i as Integer i = Cint(myDataSet.Tables("MyTable").Row(0).("MyValue")) ProcessMyVariable(i)
Better Code:
Dim i as Integer = 0 If IsNumeric(myDataSet.Tables("MyTable").Row(0).("MyValue")) Then i = Cint(myDataSet.Tables("MyTable").Row(0).("MyValue")) End If ProcessMyVariable(i)
Best Code:
Dim i as Integer = 0 Try If myDataset.Tables.Contains("MyTable") Then If myDataSet.Tables("MyTable").Rows.Count > 0 Then If IsNumeric(myDataSet.Tables("MyTable").Row(0).("MyValue")) Then i = Cint(myDataSet.Tables("MyTable").Row(0).("MyValue")) End If End If End If Catch e as Exception End Try ProcessMyVariable(i)
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