Could not convert variant of type (Null) into type (OleStr)

Question

Do you know why the block of code bellow will negate the \"Could not convert variant of type (Null) into type (OleStr)\" on some computers, not all of them but 3 out of ten comp

Answer 1

You code fails when the value of a WMI property returns null. You can fix this, checking if the property has a null value before to cast or convert to an string. For this task you can use the VarIsNull function or just use the VarToStr method to safely convert variants to strings like so.

 LNode := ClientForm.TreeView1.Items.AddChild(Node, 
              Format('%s',[VarToStr(FWbemObject.Name)]));
 LNode2 := ClientForm.TreeView1.Items.AddChild(LNode, 
              Format('%s',[VarToStr(FWbemObject.Version)]));