IsNull in VB.net

[adwaitjoshi]

I am sorry I am new to vb.net I am working on some code written in C# I check for some variables if they are null. In vb I used to use variable = vbNull in C# I am using IsNull(Variable) but vb.net doesnt have the IsNull. Instead the IDE tells me to use IsDBNull is this same as IsNull? Or whats better to use?

Second question I have is does vb.net have a ternary operator?

(condition?"if true":"if false")

 

[kulrom]

You have two options:

[SIZE=2][COLOR=#0000ff]If[/COLOR][/SIZE][SIZE=2] IsDBNull(cmd.ExecuteScalar) = [/SIZE][SIZE=2][COLOR=#0000ff]True [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Then[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]{...}
[/COLOR][/SIZE]

or

[SIZE=2][COLOR=#0000ff]If[/COLOR][/SIZE][SIZE=2] cmd.ExecuteScalar [/SIZE][SIZE=2][COLOR=#0000ff]Is[/COLOR][/SIZE][SIZE=2] DBNull.Value = [/SIZE][SIZE=2][COLOR=#0000ff]True [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Then [COLOR=darkgreen]'you can save up to 40% of the resources in this way[/COLOR][/COLOR][/SIZE]
[COLOR=#006400]{...}[/COLOR]

Regards

 

[adwaitjoshi]

Are IsDBNull and IsNull same? Is DBNull.value same as any other null value? Why is it called "DB" null

 

[kulrom]

please read this it will clarify a lot of things to you

http://www.asptoday.com/Content.aspx?id=2371
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vsintro7/html/vxgrfLanguageEquivalents.asp

Regards

 

[kulrom]

I noticed that you are not satisfied with the answer so i will try to add couple words yet. Yes isDBNull is the same with its C# equivalent isNull when you check for values fetched from DB.
i.e.

VB.NET:

If not IsDBNull(dr("somefield") Then 
myValue = dr("somefield") 
End If

C# .NET:

if (!dr.IsNull("somefield"){ 
myValue = dr["somefield"].ToString(); 
}

Regards

btw, if you try to use isNULL with VB.NET ... vs.net intellisense will tell you that IsNull is not supported and to use DBNull instead.

 

[adwaitjoshi]

thanks a lot

 

[kulrom]

Does it mean that we answered your question? In that case i am happy that i was of help

 

[adwaitjoshi]

yes you did.

 

[jmcilhinney]

Moved to more appropriate forum.

You can also use:

If TypeOf object Is DBNull Then

VB.NET has no ternary operator. You can use the IIf function but it is a function and not an operator, so it is similar but not the same. The first difference is that it is not as efficient because it involves a function call. The second, more important difference is that both the True and False conditions are evaluated in all cases, while the C# operator does not evaluate the False condition if the expression is True. Forgetting this in VB.NET can lead to unexpected results or unhandled exceptions in some circumstances.