Code

Re: Using the "IsNothing" keyword

DuneBug — Fri, 16 Feb 2007 20:07:17 GMT

I don't know what coding interface you are using (VB.net or the built-in infopath script.
you might try this:

dim obj as object

if not obj is nothing then
' do blah
end if

"Is" is the comparison operator for reference types. Using it is the same thing as saying "if obj = nothing" except since obj and nothing are both reference types the "=" and "<>" operators won't work.

Give it a shot, I hope it works. If it doesn't oh well, i gave it the old college try.

Re: Using the "IsNothing" keyword

snufse — Fri, 16 Feb 2007 13:30:50 GMT

Patrick:

Is there a way to ask Microsoft? Do you have a reference site I could use? Thanks.

Re: Using the "IsNothing" keyword

Patrick Halstead — Fri, 16 Feb 2007 08:58:58 GMT

Hi Rolf,
Sorry, but I don't know. Could be something to do with the limitations of the dataset. InfoPath supports them, but there are limitations. I don't have confidence that it is a dataset issue, though.

Re: Using the "IsNothing" keyword

snufse — Thu, 15 Feb 2007 14:42:54 GMT

I have a windows app (code below) and works fine. In InfoPath 2007 gives me syntax error??????

If Not IsNothing(MyDataSet) Then
If MyDataSet.Tables("Table").Rows.Count > 0 Then
TextBox1.Text = MyDataSet.Tables("Table").Rows(0).Item(1)
TextBox2.Text = MyDataSet.Tables("Table").Rows(0).Item(22)
End If
End If

Also from MSDN Help

IsNothing returns True if the expression represents an object variable that currently has no object assigned to it; otherwise, it returns False.

IsNothing is intended to work on reference types. A value type cannot hold a value of Nothing and reverts to its default value if you assign Nothing to it. If you supply a value type in Expression, IsNothing always returns False.

Example
The following example uses the IsNothing function to determine if an object variable is associated with any object instance.

Visual Basic Copy Code
Dim testVar As Object
' No instance has been assigned to variable testVar yet.
Dim testCheck As Boolean
' The following call returns True.
testCheck = IsNothing(testVar)
' Assign a string instance to variable testVar.
testVar = "ABCDEF"
' The following call returns False.
testCheck = IsNothing(testVar)
' Disassociate variable testVar from any instance.
testVar = Nothing
' The following call returns True.
testCheck = IsNothing(testVar)

Re: Using the "IsNothing" keyword

Patrick Halstead — Wed, 14 Feb 2007 18:44:36 GMT

Hi Rolf,
What is "IsNothing"? Is this a built in function in VB.NET? If it is, it should be supported because InfoPath is .NET compatible.

Using the "IsNothing" keyword

snufse — Wed, 14 Feb 2007 17:25:30 GMT

I my code behind I am using the "IsNothing" keyword and it gives an error: "Name "IsnNothing" is not declared". Is this not supported by InfoPath through the programming interface????

If Not IsNothing(MyDataSet) Then
If MyDataSet.Tables("Table").Rows.Count > 0 Then
myNav.SelectSingleNode("//my:name", Me.NamespaceManager). _
SetValue(MyDataSet.Tables("Table").Rows(0).Item(1))
myNav.SelectSingleNode("//my:department", Me.NamespaceManager). _
SetValue(MyDataSet.Tables("Table").Rows(0).Item(22))
End If
End If