The .NET API allows
you to cast an object from one type to another. This is necessary when
iterating objects in a collection that has multiple types and you only want
to work with a certain type in that collection. For examplethrough the
modelspace blockTableRecord and you want to do something only with the
BlockReferences. The code would test to see if the type of entity is a
BlockReference lets say the code is
iterating and if it is, it would cast that entity to a BlockReference. In
Visual Basic casting is done using the Ctype function. Notice that this
function takes the object for the first argument, and a type for the second
argument. In C# you use the Type in
parentheses to cast the entity to the object on the left side of the equals
sign. You can also use the as operator and then test to make sure the object
is not null. The is operator can also be helpful to test the type of the
object. |