How to check for a Null value in VB NET

Question

I have this   If String IsNullOrEmpty editTransactionRow pay id ToString      False Then     stTransactionPaymentID   editTransactionRow pay id  Check for null value End If   Now  when editTransactionRow pay id is Null Visual Basic throws an exception  Is there something wrong with this code

User · Accepted Answer

If you are using a strongly-typed dataset then you should do this:

If Not ediTransactionRow.Ispay_id1Null Then
    'Do processing here
End If

You are getting the error because a strongly-typed data set retrieves the underlying value and exposes the conversion through the property. For instance, here is essentially what is happening:

Public Property pay_Id1 Then
   Get
     return DirectCast(me.GetValue("pay_Id1", short)
   End Get
   'Abbreviated for clarity
End Property

The GetValue method is returning DBNull which cannot be converted to a short.

User · Answer

If Not editTransactionRow pay id AndAlso String IsNullOrEmpty editTransactionRow pay id ToString      False Then     stTransactionPaymentID   editTransactionRow pay id  Check for null value End If

User · Answer

If Short TryParse editTransactionRow pay id  New Short  Then editTransactionRow pay id ToString

User · Answer

If Not editTransactionRow pay id AndAlso String IsNullOrEmpty editTransactionRow pay id ToString      False Then     stTransactionPaymentID   editTransactionRow pay id  Check for null value End If

User · Answer

editTransactionRow pay id is Null so in fact you are doing  null ToString   and it cannot be executed  You need to check editTransactionRow pay id and not editTransactionRow pay id ToString     You code should be  IF pay id is a string    If String IsNullOrEmpty editTransactionRow pay id    False Then     stTransactionPaymentID   editTransactionRow pay id  Check for null value End If   If pay id is an Integer than you can just check if it s null normally without String    Edit to show you if it s not a String   If editTransactionRow pay id IsNot Nothing Then     stTransactionPaymentID   editTransactionRow pay id  Check for null value End If   If it s from a database you can use IsDBNull but if not  do not use it

User · Answer

You can also use the IsDBNull function   If Not IsDBNull editTransactionRow pay id  Then

User · Answer

The equivalent of null in VB is Nothing so your check wants to be   If editTransactionRow pay id IsNot Nothing Then     stTransactionPaymentID   editTransactionRow pay id End If   Or possibly  if you are actually wanting to check for a SQL null value   If editTransactionRow pay id  lt  gt  DbNull Value Then         End If

User · Answer

If Short TryParse editTransactionRow pay id  New Short  Then editTransactionRow pay id ToString

User · Answer

You have to check to ensure editTransactionRow is not null and pay id is not null

User · Answer

editTransactionRow pay id is Null so in fact you are doing  null ToString   and it cannot be executed  You need to check editTransactionRow pay id and not editTransactionRow pay id ToString     You code should be  IF pay id is a string    If String IsNullOrEmpty editTransactionRow pay id    False Then     stTransactionPaymentID   editTransactionRow pay id  Check for null value End If   If pay id is an Integer than you can just check if it s null normally without String    Edit to show you if it s not a String   If editTransactionRow pay id IsNot Nothing Then     stTransactionPaymentID   editTransactionRow pay id  Check for null value End If   If it s from a database you can use IsDBNull but if not  do not use it

User · Answer

If Not IsDBNull dr 0   Then     use dr 0  End If   Don t use   Nothing or Is Nothing  because it fails to check if the datarow value is null or not  I tried  and I make sure the above code worked

User · Answer

If Not editTransactionRow pay id AndAlso String IsNullOrEmpty editTransactionRow pay id ToString      False Then     stTransactionPaymentID   editTransactionRow pay id  Check for null value End If

User · Answer

The equivalent of null in VB is Nothing so your check wants to be   If editTransactionRow pay id IsNot Nothing Then     stTransactionPaymentID   editTransactionRow pay id End If   Or possibly  if you are actually wanting to check for a SQL null value   If editTransactionRow pay id  lt  gt  DbNull Value Then         End If

User · Answer

I find the safest way is   If Not editTransactionRow pay id Is Nothing   It might read terribly  but the ISIL is actually very different from IsNot Nothing  and it doesn t try and evaluate the expression  which could give a null reference exception

User · Answer

This is the exact answer  Try this code   If String IsNullOrEmpty editTransactionRow pay id ToString      False Then     stTransactionPaymentID   editTransactionRow pay id  Check for null value End If

User · Answer

If Not IsDBNull dr 0   Then     use dr 0  End If   Don t use   Nothing or Is Nothing  because it fails to check if the datarow value is null or not  I tried  and I make sure the above code worked

User · Answer

If Short TryParse editTransactionRow pay id  New Short  Then editTransactionRow pay id ToString

User · Answer

If Short TryParse editTransactionRow pay id  New Short  Then editTransactionRow pay id ToString

User · Answer

I find the safest way is   If Not editTransactionRow pay id Is Nothing   It might read terribly  but the ISIL is actually very different from IsNot Nothing  and it doesn t try and evaluate the expression  which could give a null reference exception

User · Answer

You have to check to ensure editTransactionRow is not null and pay id is not null

User · Answer

The equivalent of null in VB is Nothing so your check wants to be   If editTransactionRow pay id IsNot Nothing Then     stTransactionPaymentID   editTransactionRow pay id End If   Or possibly  if you are actually wanting to check for a SQL null value   If editTransactionRow pay id  lt  gt  DbNull Value Then         End If

User · Answer

This is the exact answer  Try this code   If String IsNullOrEmpty editTransactionRow pay id ToString      False Then     stTransactionPaymentID   editTransactionRow pay id  Check for null value End If

User · Answer

You can also use the IsDBNull function   If Not IsDBNull editTransactionRow pay id  Then

User · Answer

editTransactionRow pay id is Null so in fact you are doing  null ToString   and it cannot be executed  You need to check editTransactionRow pay id and not editTransactionRow pay id ToString     You code should be  IF pay id is a string    If String IsNullOrEmpty editTransactionRow pay id    False Then     stTransactionPaymentID   editTransactionRow pay id  Check for null value End If   If pay id is an Integer than you can just check if it s null normally without String    Edit to show you if it s not a String   If editTransactionRow pay id IsNot Nothing Then     stTransactionPaymentID   editTransactionRow pay id  Check for null value End If   If it s from a database you can use IsDBNull but if not  do not use it

User · Answer

If Not editTransactionRow pay id AndAlso String IsNullOrEmpty editTransactionRow pay id ToString      False Then     stTransactionPaymentID   editTransactionRow pay id  Check for null value End If

User · Answer

You have to check to ensure editTransactionRow is not null and pay id is not null

User · Answer

You have to check to ensure editTransactionRow is not null and pay id is not null

User · Answer

The equivalent of null in VB is Nothing so your check wants to be   If editTransactionRow pay id IsNot Nothing Then     stTransactionPaymentID   editTransactionRow pay id End If   Or possibly  if you are actually wanting to check for a SQL null value   If editTransactionRow pay id  lt  gt  DbNull Value Then         End If

User · Answer

editTransactionRow pay id is Null so in fact you are doing  null ToString   and it cannot be executed  You need to check editTransactionRow pay id and not editTransactionRow pay id ToString     You code should be  IF pay id is a string    If String IsNullOrEmpty editTransactionRow pay id    False Then     stTransactionPaymentID   editTransactionRow pay id  Check for null value End If   If pay id is an Integer than you can just check if it s null normally without String    Edit to show you if it s not a String   If editTransactionRow pay id IsNot Nothing Then     stTransactionPaymentID   editTransactionRow pay id  Check for null value End If   If it s from a database you can use IsDBNull but if not  do not use it

[vb.net] How to check for a Null value in VB.NET

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