Partager via

Viewing Type Information

  • Article

The System.Type class is central to reflection. The common language runtime creates the Type for a loaded type when reflection requests it. You can use a Type object's methods, fields, properties, and nested classes to find out everything about that type.

Use Assembly.GetType or Assembly.GetTypes to obtain Type objects from assemblies that have not been loaded, passing in the name of the type or types you want. Use Type.GetType to get the Type objects from an assembly that is already loaded. Use Module.GetType and Module.GetTypes to obtain module Type objects.

The following example shows the syntax necessary to get the Assembly object and module for an assembly.

' Gets the mscorlib assembly in which the object is defined.
Dim a As Reflection.Assembly = GetType(Object).Module.Assembly
[C#]
// Gets the mscorlib assembly in which the object is defined.
Assembly a = typeof(Object).Module.Assembly;

The following example demonstrates getting Type objects from a loaded assembly.

' Loads an assembly using its file name.
Dim a As Reflection.Assembly = Reflection.Assembly.LoadFrom("MyExe.exe")
' Gets the type names from the assembly.
Dim types2 As Type() = a.GetTypes()
Dim t As Type
For Each t In  types2
    Console.WriteLine(t.FullName)
Next t
[C#]
// Loads an assembly using its file name.
Assembly a = Assembly.LoadFrom ("MyExe.exe");
// Gets the type names from the assembly.
Type [] types2 = a.GetTypes ();
foreach (Type t in types2)
{
    Console.WriteLine (t.FullName);
}

Once you obtain a Type, there are many ways you can discover information about the members of that type. For example, you can find out about all the type's members by calling the Type.GetMembers method, which obtains an array of MemberInfo objects describing each of the members of the current type.

You can also use methods on the Type class to retrieve information about one or more constructors, methods, events, fields, or properties that you specify by name. For example, Type.GetConstructor encapsulates a specific constructor of the current class.

If you have a Type, you can use the Type.Module property to obtain an object that encapsulates the module containing that type. Use the Module.Assembly property to locate an object that encapsulates the assembly containing the module. You can obtain the assembly that encapsulates the type directly by using the Type.Assembly property.

System.Type and ConstructorInfo

The following example shows how to list the constructors for a class, in this case, the String class.

' This program lists all the public constructors 
' of the System.String class.
Imports System
Imports System.Reflection
Class ListMembers
    Public Shared Sub Main()
        Dim t As Type = GetType(String)
        Console.WriteLine("Listing all the public constructors of the {0} type", t)
        ' Constructors.
        Dim ci As ConstructorInfo() = t.GetConstructors((BindingFlags.Public Or BindingFlags.Instance))
        Console.WriteLine("//Constructors")
        PrintMembers(ci)
    End Sub
    Public Shared Sub PrintMembers(ms() As MemberInfo)
        Dim m As MemberInfo
        For Each m In ms
            Console.WriteLine("{0}{1}", "     ", m)
        Next m
        Console.WriteLine()
    End Sub
End Class
[C#]
// This program lists all the public constructors 
// of the System.String class.
using System;
using System.Reflection;
class ListMembers {
    public static void Main(String[] args) {
        Type t = typeof(System.String);
        Console.WriteLine ("Listing all the public constructors of the {0} type", t);
        // Constructors.
        ConstructorInfo[] ci = t.GetConstructors(BindingFlags.Public | BindingFlags.Instance);
        Console.WriteLine ("//Constructors");
        PrintMembers (ci);
    }
    public static void PrintMembers(MemberInfo [] ms) {
        foreach (MemberInfo m in ms) {
            Console.WriteLine ("{0}{1}", "     ", m);
        }
        Console.WriteLine();
    }
}

MemberInfo, MethodInfo, FieldInfo, and PropertyInfo

Obtain information about the type's methods, properties, events, and fields using MemberInfo, MethodInfo, FieldInfo, or PropertyInfo objects.

The following example uses MemberInfo to list the number of members in the System.IO.File class and uses the System.Type.IsPublic property to determine the visibility of the class.

Option Explicit
Option Strict
Imports System
Imports System.IO
Imports System.Reflection
Imports Microsoft.VisualBasic
Class Mymemberinfo
    Public Shared Sub Main()
        Console.WriteLine(ControlChars.Cr & "Reflection.MemberInfo")
        ' Gets the Type and MemberInfo.
        Dim MyType As Type = Type.GetType("System.IO.File")
        Dim Mymemberinfoarray As MemberInfo() = MyType.GetMembers()
        ' Gets and displays the DeclaringType method. 
        Console.WriteLine(ControlChars.Cr & "There are {0} members in {1}.", Mymemberinfoarray.Length, MyType.FullName)
        Console.WriteLine("{0}.", MyType.FullName)
        If MyType.IsPublic Then
            Console.WriteLine("{0} is public.", MyType.FullName)
        End If
    End Sub
End Class
[C#]
using System;
using System.IO;
using System.Reflection;

class Mymemberinfo
{ 
    public static void Main(string[] args)
    { 
        Console.WriteLine ("\nReflection.MemberInfo");
        // Gets the Type and MemberInfo.
        Type MyType =Type.GetType("System.IO.File");
        MemberInfo[] Mymemberinfoarray = MyType.GetMembers(); 
        // Gets and displays the DeclaringType method. 
        Console.WriteLine("\nThere are {0} members in {1}.", 
            Mymemberinfoarray.Length, MyType.FullName);
        Console.WriteLine("{0}.", MyType.FullName); 
        if (MyType.IsPublic)
        {
            Console.WriteLine("{0} is public.", MyType.FullName);
        }
    }
}

The following example investigates the type of the specified member. It performs reflection on a member of the MemberInfo class, and lists its type.

' This code displays information about the GetValue method of FieldInfo.
Option Explicit
Option Strict
Imports System
Imports System.Reflection
Class MyMethodInfo
    Public Shared Sub Main()
        Console.WriteLine("Reflection.MethodInfo")
        ' Gets and displays the Type.
        Dim MyType As Type = Type.GetType("System.Reflection.FieldInfo")
        ' Specifies the member for which you want type information.
        Dim Mymethodinfo As MethodInfo = MyType.GetMethod("GetValue")
        Console.WriteLine((MyType.FullName & "." & Mymethodinfo.Name))
        ' Gets and displays the MemberType property.
        Dim Mymembertypes As MemberTypes = Mymethodinfo.MemberType
        If MemberTypes.Constructor = Mymembertypes Then
            Console.WriteLine("MemberType is of type All")
        ElseIf MemberTypes.Custom = Mymembertypes Then
            Console.WriteLine("MemberType is of type Custom")
        ElseIf MemberTypes.Event = Mymembertypes Then
            Console.WriteLine("MemberType is of type Event")
        ElseIf MemberTypes.Field = Mymembertypes Then
            Console.WriteLine("MemberType is of type Field")
        ElseIf MemberTypes.Method = Mymembertypes Then
            Console.WriteLine("MemberType is of type Method")
        ElseIf MemberTypes.Property = Mymembertypes Then
            Console.WriteLine("MemberType is of type Property")
        ElseIf MemberTypes.TypeInfo = Mymembertypes Then
            Console.WriteLine("MemberType is of type TypeInfo")
        End If
        Return
    End Sub
End Class
[C#]
// This code displays information about the GetValue method of FieldInfo.
using System;
using System.Reflection;
class MyMethodInfo {
    public static int Main() {
        Console.WriteLine("Reflection.MethodInfo");
        // Gets and displays the Type.
        Type MyType = Type.GetType("System.Reflection.FieldInfo");
        // Specifies the member for which you want type information.
        MethodInfo Mymethodinfo = MyType.GetMethod("GetValue");
        Console.WriteLine(MyType.FullName + "." + Mymethodinfo.Name);
        // Gets and displays the MemberType property.
        MemberTypes Mymembertypes = Mymethodinfo.MemberType;
        if (MemberTypes.Constructor == Mymembertypes) {
            Console.WriteLine("MemberType is of type All"); 
        }
        else if (MemberTypes.Custom == Mymembertypes) {
            Console.WriteLine("MemberType is of type Custom"); 
        }
        else if (MemberTypes.Event == Mymembertypes) {
            Console.WriteLine("MemberType is of type Event"); 
        }
        else if (MemberTypes.Field == Mymembertypes) {
            Console.WriteLine("MemberType is of type Field"); 
        }
        else if (MemberTypes.Method == Mymembertypes) {
            Console.WriteLine("MemberType is of type Method"); 
        }
        else if (MemberTypes.Property == Mymembertypes) {
            Console.WriteLine("MemberType is of type Property"); 
        }
        else if (MemberTypes.TypeInfo == Mymembertypes) {
            Console.WriteLine("MemberType is of type TypeInfo"); 
        }
        return 0;
    }
}

The following example uses all the Reflection *Info classes along with BindingFlags to list all the members (constructors, fields, properties, events, and methods) of the specified class, dividing the members into static and instance categories.

' This program lists all the members of the 
' System.IO.BufferedStream class.
Imports System
Imports System.IO
Imports System.Reflection
Imports Microsoft.VisualBasic
Class ListMembers
    Public Shared Sub Main()
        ' Specifies the class.
        Dim t As Type = GetType(System.IO.BufferedStream)
        Console.WriteLine("Listing all the members (public and non public) of the {0} type", t)
        ' Lists static fields first.
        Dim fi As FieldInfo() = t.GetFields((BindingFlags.Static Or BindingFlags.NonPublic Or BindingFlags.Public))
        Console.WriteLine("// Static Fields")
        PrintMembers(fi)
        ' Static properties.
        Dim pi As PropertyInfo() = t.GetProperties((BindingFlags.Static Or BindingFlags.NonPublic Or BindingFlags.Public))
        Console.WriteLine("// Static Properties")
        PrintMembers(pi)
        ' Static events.
        Dim ei As EventInfo() = t.GetEvents((BindingFlags.Static Or BindingFlags.NonPublic Or BindingFlags.Public))
        Console.WriteLine("// Static Events")
        PrintMembers(ei)
        ' Static methods.
        Dim mi As MethodInfo() = t.GetMethods((BindingFlags.Static Or BindingFlags.NonPublic Or BindingFlags.Public))
        Console.WriteLine("// Static Methods")
        PrintMembers(mi)
        ' Constructors.
        Dim ci As ConstructorInfo() = t.GetConstructors((BindingFlags.Instance Or BindingFlags.NonPublic Or BindingFlags.Public))
        Console.WriteLine("// Constructors")
        PrintMembers(ci)
        ' Instance fields.
        fi = t.GetFields((BindingFlags.Instance Or BindingFlags.NonPublic Or BindingFlags.Public))
        Console.WriteLine("// Instance Fields")
        PrintMembers(fi)
        ' Instance properites.
        pi = t.GetProperties((BindingFlags.Instance Or BindingFlags.NonPublic Or BindingFlags.Public))
        Console.WriteLine("// Instance Properties")
        PrintMembers(pi)
        ' Instance events.
        ei = t.GetEvents((BindingFlags.Instance Or BindingFlags.NonPublic Or BindingFlags.Public))
        Console.WriteLine("// Instance Events")
        PrintMembers(ei)
        ' Instance methods.
        mi = t.GetMethods((BindingFlags.Instance Or BindingFlags.NonPublic Or BindingFlags.Public))
        Console.WriteLine("// Instance Methods")
        PrintMembers(mi)
        Console.WriteLine(ControlChars.CrLf & "Press ENTER to exit.")
        Console.Read()
    End Sub
    Public Shared Sub PrintMembers(ms() As MemberInfo)
        Dim m As MemberInfo
        For Each m In  ms
            Console.WriteLine("{0}{1}", "     ", m)
        Next m
        Console.WriteLine()
    End Sub
End Class
[C#]
// This program lists all the members of the 
// System.IO.BufferedStream class.
using System;
using System.IO;
using System.Reflection;

class ListMembers {
    public static void Main(String[] args) {
        // Specifies the class.
        Type t = typeof (System.IO.BufferedStream);
        Console.WriteLine ("Listing all the members (public and non public) of the {0} type", t);

        // Lists static fields first.
        FieldInfo [] fi = t.GetFields (BindingFlags.Static | 
         BindingFlags.NonPublic | BindingFlags.Public);
        Console.WriteLine ("// Static Fields");
        PrintMembers (fi);

        // Static properties.
        PropertyInfo [] pi = t.GetProperties (BindingFlags.Static | 
         BindingFlags.NonPublic | BindingFlags.Public);
        Console.WriteLine ("// Static Properties");
        PrintMembers (pi);

        // Static events.
        EventInfo [] ei = t.GetEvents (BindingFlags.Static | 
         BindingFlags.NonPublic | BindingFlags.Public);
        Console.WriteLine ("// Static Events");
        PrintMembers (ei);

        // Static methods.
        MethodInfo [] mi = t.GetMethods (BindingFlags.Static | 
         BindingFlags.NonPublic | BindingFlags.Public);
        Console.WriteLine ("// Static Methods");
        PrintMembers (mi);

        // Constructors.
        ConstructorInfo [] ci = t.GetConstructors (BindingFlags.Instance | 
         BindingFlags.NonPublic | BindingFlags.Public);
        Console.WriteLine ("// Constructors");
        PrintMembers (ci);

        // Instance fields.
        fi = t.GetFields (BindingFlags.Instance | BindingFlags.NonPublic | 
         BindingFlags.Public);
        Console.WriteLine ("// Instance Fields");
        PrintMembers (fi);

        // Instance properites.
        pi = t.GetProperties (BindingFlags.Instance | BindingFlags.NonPublic | 
         BindingFlags.Public);
        Console.WriteLine ("// Instance Properties");
        PrintMembers (pi);

        // Instance events.
        ei = t.GetEvents (BindingFlags.Instance | BindingFlags.NonPublic | 
         BindingFlags.Public);
        Console.WriteLine ("// Instance Events");
        PrintMembers (ei);

        // Instance methods.
        mi = t.GetMethods (BindingFlags.Instance | BindingFlags.NonPublic   
         | BindingFlags.Public);
        Console.WriteLine ("// Instance Methods");
        PrintMembers (mi);

        Console.WriteLine ("\r\nPress ENTER to exit.");
        Console.Read();
    }

    public static void PrintMembers (MemberInfo [] ms) {
        foreach (MemberInfo m in ms) {
            Console.WriteLine ("{0}{1}", "     ", m);
        }
        Console.WriteLine();
    }
}

See Also

Viewing Type Information | BindingFlags | Assembly.GetType | Assembly.GetTypes | Type.GetType | Type.GetMembers | Type.GetFields | Module.GetType | Module.GetTypes | MemberInfo | ConstructorInfo | MethodInfo | FieldInfo | EventInfo | ParameterInfo