How to check if an object is a certain type

Question

I am passing various objects to a subroutine to run the same process but using a different object each time  For example  in one case I am using a ListView and in another case I am passing a DropDownList   I want to check if the object being passed is a DropDownList then execute some code if it is  How do I do this   My code so far which doesn t work   Sub FillCategories ByVal Obj As Object      Dim cmd As New SqlCommand  sp Resources Categories   Conn      cmd CommandType   CommandType StoredProcedure     Obj DataSource   cmd ExecuteReader     If Obj Is System Web UI WebControls DropDownList Then      End If     Obj DataBind   End Sub

User · Accepted Answer

In VB NET  you need to use the GetType method to retrieve the type of an instance of an object  and the GetType   operator to retrieve the type of another known type   Once you have the two types  you can simply compare them using the Is operator   So your code should actually be written like this   Sub FillCategories ByVal Obj As Object      Dim cmd As New SqlCommand  sp Resources Categories   Conn      cmd CommandType   CommandType StoredProcedure     Obj DataSource   cmd ExecuteReader     If Obj GetType   Is GetType System Web UI WebControls DropDownList  Then      End If     Obj DataBind   End Sub   You can also use the TypeOf operator instead of the GetType method   Note that this tests if your object is compatible with the given type  not that it is the same type  That would look like this   If TypeOf Obj Is System Web UI WebControls DropDownList Then  End If     Totally trivial  irrelevant nitpick  Traditionally  the names of parameters are camelCased  which means they always start with a lower-case letter  when writing  NET code  either VB NET or C    This makes them easy to distinguish at a glance from classes  types  methods  etc

User · Answer

Some more details in relation with the response from Cody Gray  As it took me some time to digest it I though it might be usefull to others   First  some definitions    There are TypeNames  which are string representations of the type of an object  interface  etc  For example  Bar is a TypeName in Public Class Bar  or in Dim Foo as Bar  TypeNames could be seen as  labels  used in the code to tell the compiler which type definition to look for in a dictionary where all available types would be described  There are System Type objects which contain a value  This value indicates a type   just like a String would take some text or an Int would take a number  except we are storing types instead of text or numbers  Type objects contain the type definitions  as well as its corresponding TypeName    Second  the theory    Foo GetType   returns a Type object which contains the type for the variable Foo  In other words  it tells you what Foo is an instance of  GetType Bar  returns a Type object which contains the type for the TypeName Bar  In some instances  the type an object has been Cast to is different from the type an object was first instantiated from  In the following example  MyObj is an Integer cast into an Object   Dim MyVal As Integer   42 Dim MyObj As Object   CType MyVal  Object    So  is MyObj of type Object or of type Integer  MyObj GetType   will tell you it is an Integer    But here comes the Type Of Foo Is Bar feature  which allows you to ascertain a variable Foo is compatible with a TypeName Bar  Type Of MyObj Is Integer and  Type Of MyObj Is Object will both return True  For most cases  TypeOf will indicate a variable is compatible with a TypeName if the variable is of that Type or a Type that derives from it   More info here  https   docs microsoft com en-us dotnet visual-basic language-reference operators typeof-operator remarks   The test below illustrate quite well the behaviour and usage of each of the mentionned keywords and properties   Public Sub TestMethod1        Dim MyValInt As Integer   42     Dim MyValDble As Double   CType MyValInt  Double      Dim MyObj As Object   CType MyValDble  Object       Debug Print MyValInt GetType ToString   Returns System Int32     Debug Print MyValDble GetType ToString   Returns System Double     Debug Print MyObj GetType ToString   Returns System Double      Debug Print MyValInt GetType GetType ToString   Returns System RuntimeType     Debug Print MyValDble GetType GetType ToString   Returns System RuntimeType     Debug Print MyObj GetType GetType ToString   Returns System RuntimeType      Debug Print GetType Integer  GetType ToString   Returns System RuntimeType     Debug Print GetType Double  GetType ToString   Returns System RuntimeType     Debug Print GetType Object  GetType ToString   Returns System RuntimeType      Debug Print MyValInt GetType   GetType Integer      Returns True     Debug Print MyValInt GetType   GetType Double    Returns False     Debug Print MyValInt GetType   GetType Object    Returns False      Debug Print MyValDble GetType   GetType Integer    Returns False     Debug Print MyValDble GetType   GetType Double      Returns True     Debug Print MyValDble GetType   GetType Object    Returns False      Debug Print MyObj GetType   GetType Integer    Returns False     Debug Print MyObj GetType   GetType Double      Returns True     Debug Print MyObj GetType   GetType Object    Returns False      Debug Print TypeOf MyObj Is Integer   Returns False     Debug Print TypeOf MyObj Is Double     Returns True     Debug Print TypeOf MyObj Is Object     Returns True   End Sub     EDIT  You can also use Information TypeName Object  to get the TypeName of a given object  For example   Dim Foo as Bar Dim Result as String Result   TypeName Foo  Debug Print Result   Will display  Bar

[.net] How to check if an object is a certain type

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