How can DBNull not equal DBNull

c# .net object null dbnull
Refracted Paladin picture Refracted Paladin · Jan 13, 2010 · Viewed 9k times · Source

I have the following line of code

if (DBNull.Value.Equals(o) || o != null)

where o is object o in row.ItemArray I keep getting an error of -->

Xml type "List of xdt:untypedAtomic" does not support a conversion from Clr type "DBNull" to Clr type "String".

What I don't understand is that when I step through my code this if should be catching this and performing my alternate action but it does not?

Can someone please shed some light for me.

Thank you!

Answer

Tj Kellie picture Tj Kellie · Jan 13, 2010

I think you problem is that in fact

DBNull.Value == null 
//is always false

The DBNull is a special class for comparisons on values returned from the dB so you actualy need to check for a null condition AND a DBNull.value if your array contains both.

EDIT: Sorry looking closer at your code you may just need to reverse your OR operation. If o == null your first statement will blow up with your exception. Try:

if (o != null || o == DBNull.Value)

Related questions

How to do ToString for a possibly null object?

Is there a simple way of doing the following: String s = myObj == null ? "" : myObj.ToString(); I know I can do the following, but I really consider it as a hack: String s = "" + myObj; It would be great if Convert.ToString() …

Read More
Convert any object to a byte[]

I am writing a prototype TCP connection and I am having some trouble homogenizing the data to be sent. At the moment, I am sending nothing but strings, but in the future we want to be able to send any …

Read More
How to access property of anonymous type in C#?

I have this: List<object> nodes = new List<object>(); nodes.Add( new { Checked = false, depth = 1, id = "div_" + d.Id }); ... and I'm wondering if I can then grab the "Checked" property of the anonymous object. I'm not …

Read More