Introduction to .NET for ArcObjects developers

In this topic

• Introduction to the .NET Framework
• Choosing a language (VB .NET vs. C#)
• Quick guide to .NET
  • Namespaces
  • Assemblies
  • Classes
  • Class destruction and garbage collection
  • Inheritance
  • .NET interfaces
  • Access modifiers
  • Overloading and overriding 

• Working in Visual Studio
  • Introduction to the Visual Studio application files
  • Differences from the VB6 environment

Introduction to the .NET Framework

• Base Class library
• Common Language Runtime (CLR)

Choosing a language (VB .NET vs. C#)

Quick guide to .NET

Namespaces

using ESRI.ArcGIS.Controls;

Imports ESRI.ArcGIS.Controls

Assemblies

Classes

public class Animal
{
    int m_numerOfLegs;
    bool m_isAlive;

    public Animal()
    {
        m_isAlive=true;
        m_numberOfLegs=4;
    }

    public Animal(int legCount, bool living)
    {
        m_isAlive=living;
        m_numberOfLegs=legCount;
    }

    public int LegCount
    {
        get
        {
            return m_numberOfLegs;
        }
        set
        {
            m_numberOfLegs=value;
        }
    }
}

Public Class Animal
    Private m_numerOfLegs As Integer
    Private m_isAlive As Boolean
    
    Public Sub New()
        m_isAlive=True
        m_numberOfLegs=4
    End Sub
    
    Public Sub New(ByVal legCount As Integer, ByVal living As Boolean)
        m_isAlive=living;
        m_numberOfLegs=legCount
    End Sub
    
    Public Property LegCount() As Integer
        Get
        Return m_numberOfLegs
        End Get
        Set(ByVal Value As Integer)
        m_numberOfLegs=Value
        End Set
    End Property

End Class

// To define the class.
class MyMap
{
    // An instance member.
    public int mapCount;

    // A static member.
    static SaveFile(string file, string contents)
    {
        System.IO.File.WriteAllText(file, "This is file " + file + "\r\n\r\n" +
            contents);
    }
}

// To use the class's static member.
MyMap.SaveFile("myfile.txt", "here are contents");

// To use the class's instance member.
MyMap thismap=new MyMap();
thismap.mapCount=3;

' To define the class.
Friend Class MyMap
' An instance member.
Public mapCount As Integer

' A static member.

Private Function SaveFile(ByVal File As String, ByVal contents As String) As [Shared]
    System.IO.File.WriteAllText(File, "This is file " & File & Constants.vbCrLf & Constants.vbCrLf & contents)
End Function

End Class

' To use the class's static member.
MyMap.SaveFile("myfile.txt", "here are contents")

'To use the class's instance member.
Dim thismap As New MyMap()
thismap.mapCount=3

Class destruction and garbage collection

class Animal
{
    public Animal(){}

    ~Animal(){}
}

Friend Class Animal

Public Sub New()
End Sub

Protected Overrides Sub Finalize()
End Sub

End Class

Inheritance

public class Dog: Animal

Public Class Dog Inherits Animal

.NET interfaces

public interface IBark
{
    void Bark();
}

Public Interface IBark

Sub Bark()
    End Interface

public class Dog: IBark, IRun

Public Class Dog Implements IBark, IRun

Access modifiers

• public(C#) or Public (VB .NET)—No restrictions as long as the containing assembly is referenced.
• private (C#) or Private (VB .NET)—Only accessible by code in the same class.
• protected (C#) or Protected (VB .NET)—Only accessible by code in the same class or a derived class.
• internal (C#) or Friend (VB .NET)—Only accessible by any code in the same assembly.
• protected internal (C#) or Protected Friend (VB .NET)—Only accessible by code in the same assembly or a derived class in another assembly.

Overloading and overriding

class Map
{
    void AddData(Point p){}

    void AddData(Polygon p){}
}

Friend Class Map

Private Sub AddData(ByVal p As Point)
End Sub

Private Sub AddData(ByVal p As Polygon)
End Sub

End Class

class Animal
{
    public abstract void Speak();
}

class Dog: Animal
{
    public override void Speak()
    {
        Bark();
    }
}

Friend Class Animal
Public MustOverride Sub Speak()
End Class

Friend Class Dog
Inherits Animal
Public Overrides Sub Speak()
Bark()
End Sub

End Class

Naming conventions

• Use Pascal casing (capitalizing the first letter in each word) for namespaces, classes, members, and constants. See the following code example:
  

const string MapUnits="meters";

Const MapUnits As String="meters"

bool isVisible;

Dim isVisible As Boolean

• Precede member variables with m_.
  

Data type conversions

double width=3.5;
int paddedWidth=(int)width;

Dim Width As Double=3.5
Dim paddedWidth As Integer
paddedWidth=CType(Width, Integer)

Changes to using variables from VB6

• VB6 used the Set keyword, while .NET does not.
• .NET supports variables defined in blocks. The variable is visibile from its definition until the end of the block (such as an if statement) that it is defined in. If it needs to be visible outside that block, its definition should be moved outside the block.
  
  See the following code example:
  

x=6;
bool overFive=false;
if (x > 5)
{
    overFive=true;
}

MessageBox.Show(overFive.ToString());

Dim x=6
Dim overFive As Boolean=False;
If x > 5
    overFive=True
End If
MessageBox.Show (overFive.ToString())

int x, y;

Dim x, y As Integer

int x=32;

Dim x As Integer=32

Changes in arguments from VB6

• When passing arguments, VB .NET and C# default to passing by value, where VB6 passed by reference.
• VB6 supported optional parameters. They are not supported in C# and instead, overloading should be used. In VB .NET, optional parameters are allowed if default values are provided.
• VB6 only required a parenthesis if a return value was expected. They are always required in C# and VB .NET.

Working in Visual Studio

Introduction to the Visual Studio application files

• Solution file (.sln)—Organizes projects.
• Project file (.vbproj or .csproj)—Stores project information and associated file lists for VB .NET and C# projects, respectively.
• Project user options file (.vbproj.user or .csproj.user)—Stores project option settings for VB .NET and C# projects, respectively.
• Code file (.vb or .cs)—Holds the VB .NET or C# code, respectively. Includes form definitions, control settings, and code procedures.
• Resource file (.resx)—Defines resources used by the form, including text strings and graphics.
• bin folder—Contains compiled code.
• obj folder—Contains files for debugging code.

Differences from the VB6 environment