In the fine, time honored tradition, I have continued to update with each new Visual Studio release and have finally done so for Visual Studio 2010.

To install, download, unzip and right click and install the INF file, it will add a “VS 2010 Cmd Prompt Here” menu item when you right click on a folder in Explorer. Clicking on the menu item will launch a DOS prompt in that directory with all of the Visual Studio and .NET paths set correctly.

• Visual Studio 2010 Command Prompt Here (x86)
• Visual Studio 2010 Command Prompt Here (x64)

This assumes that you have installed Visual Studio to the default directory on the C drive. If that is not the case, edit the INF file and change line 38 to the correct path for your installation.

return max( eRetVal, GetNumber() );

While debugging, he noticed that he was stepping into the GetNumber() method twice, and in his code, it had side-effects. We both puzzled over it for awhile. We looked at the disassembly and sure enough, it was getting called twice, but why? Then it hit me, max is a macro, not a function. If you go to the definition of max, you find;

#ifndef max
#define max(a,b)            (((a) > (b)) ? (a) : (b))
#endif

So, if you expand that macro out, the original code gets compiles as;

return (((eRetVal) > (GetNumber()) ? (eRetVal) : (GetNumber());

Once the macro is expanded, it is easy to see why the method is called twice. Obviously I have not being doing enough C++ lately. There was a time when I would have seen that immediately as it is the classic example, but I have been working in .NET so long now that I am forgetting all of the little ways that C++ can bite you.

Copier<ICustomer>.Copy( customer ).To<ICustomerView>( view );

Today, I am going to use extension methods to simplify the above code even further. I want to be able to write

customer.CopyTo<ICustomerView>( view );

or if we want to rely on type inferencing with the generic CopyTo method, you could write it as simply as

customer.CopyTo( view );

How is this done? Using extension methods, it was actually much simpler than yesterday’s Copier class. In fact, it just ended up being one line of code for the CopyTo method and for the CopyFrom method. I simply wrapped the CopyHelper class like this.

public static class CopierExtensions
{
    public static void CopyTo<T>( this object from, T to ) where T : class
    {
        CopyHelper.Copy( from.GetType(), from, typeof( T ), to );
    }

    public static void CopyFrom<T>( this object to, T from ) where T : class
    {
        CopyHelper.Copy( typeof( T ), from, to.GetType(), to );
    }
}

The only problem I have with this is that the class that the extension methods are applied to are not constrained by an interface, so all matching properties are copied. Does anyone have any ideas on that?

I have uploaded a copy of the solution for this project along with an NUnit test project. Take a look, use it if you like and feel free to give me suggestions for improvements.

In the next few posts I was thinking of extending these classes even further. I might add attributes that allow you to ignore certain properties, maybe add an attribute that specifies interfaces that you are allowed to copy to, possibly an attribute that allows properties to automatically be converted between types. What would you find useful or like to see? Would you like to see a post on the performance using these methods?

// Copy the data from the customer to the view
view.Address = customer.Address;
view.Country = customer.Country;
view.FirstName = customer.FirstName;
view.LastName = customer.LastName;
view.PostalCode = customer.PostalCode;
view.Province = customer.Province;

The newly created CopyHelper class allows me to shorten that to this.

// Copy the data from the customer to the view (using reflection in .NET 1.x)
CopyHelper.Copy( typeof(ICustomer), customer, typeof(ICustomerView), view );

Today, I want to extend that code using Generics and a fluent interface so that I can write code like this.

// Copy the data from the customer to the view (using reflection and generics in .NET 2.0)
Copier<ICustomer>.Copy( customer ).To<ICustomerView>( view );

Internally, I use my CopyHelper class from my last post. I extend that by creating a generic Copier class. I make the constructor private so that it can only be created as a part of the fluent interface, in this case the static copy method. Using the instance of the Copier class that was returned from that method, you can then copy To or From another class instance.

Here is the code.

public sealed class Copier<T1> where T1 : class
{
    #region Private Members

    private readonly T1 _subject;

    #endregion

    #region Public Interface

    /// <summary>
    /// Begin the copying process.
    /// </summary>
    /// <param name="interface1">The object you are copying from or to</param>
    /// <returns>An instance of the Copier class so that you can
    /// continue with the copy to/from in a fluent interface.</returns>
    public static Copier<T1> Copy( T1 interface1 )
    {
        return new Copier<T1>( interface1 );
    }

    #endregion

    #region Construction

    /// <summary>
    /// Private constructor so that it can only be created as a part of a fluent interface.
    /// </summary>
    /// <param name="subject"></param>
    private Copier( T1 subject )
    {
        _subject = subject;
    }

    #endregion

    #region Copier Methods

    /// <summary>
    /// Copies properties from the subject to the passed in object.
    /// </summary>
    /// <typeparam name="T2">The type of object you are copying into.</typeparam>
    /// <param name="to">The object to copy into.</param>
    /// <returns>The modified object that you passed in.</returns>
    public T2 To<T2>( T2 to ) where T2 : class
    {
        CopyHelper.Copy( typeof( T1 ), _subject, typeof( T2 ), to );
        return to;
    }

    /// <summary>
    /// Copies properties from the passed in object into the subject.
    /// </summary>
    /// <typeparam name="T2">The type of object you are copying from.</typeparam>
    /// <param name="from">The object to copy from.</param>
    /// <returns>The modified subject that you originally passed in the Copy method.</returns>
    public T1 From<T2>( T2 from ) where T2 : class
    {
        CopyHelper.Copy( typeof( T2 ), from, typeof( T1 ), _subject );
        return _subject;
    }

    #endregion
}

I would like to constrain T1 and T2 to interfaces at compile time, but I am not sure if that can be done. If you have ideas, please post them in the comments. I thought of using reflection to check if T1 and T2 are interfaces at run time, but I am a big believer in favouring compile time errors over run time errors.

In my next post, I am going to use C# 3.0 extension methods to further simplify copying allowing you to write code like this.

// Copy the data from the customer to the view (using extension methods in C# 3.0)
customer.CopyTo<ICustomerView>( view );

I am very interested in hearing your feedback on this, so be sure to post to the comments. Do you think this is a good idea? Do you have suggestions for improvements? Let me know.

// Copy the data from the customer to the view
view.Address = customer.Address;
view.Country = customer.Country;
view.FirstName = customer.FirstName;
view.LastName = customer.LastName;
view.PostalCode = customer.PostalCode;
view.Province = customer.Province;

I would much rather write something like one of the following lines;

// Copy the data from the customer to the view (using reflection in .NET 1.x)
CopyHelper.Copy( typeof(ICustomer), customer, typeof(ICustomerView), view );

// Copy the data from the customer to the view (using reflection and generics in .NET 2.0)
Copier<ICustomer>.Copy( customer ).To<ICustomerView>( view );

// Copy the data from the customer to the view (using extension methods in C# 3.0)
customer.CopyTo<ICustomerView>( view );

It got me to thinking that there must be a better way, so I began writing code that would do the grunt work for me. Too often,

Over the next few days, I will blog about my thought process in developing this method and take it through the various iterations that can be seen in lines 2, 5 & 8 above.

Today, I will start with the .NET 1.x version. I will start with some design decisions;

• I want to be able to specify the types that I am copying between, not infer them using reflection. This way, I can use the interfaces, not the concrete classes when I am copying between the objects.
• For now, I am going to assume that if both interfaces have a non-static get/set property with the same name and type I will copy between them.
• I need to check that neither object is null and that I am not trying to copy an object over to itself.

This was simple enough. I created a static helper class called CopyHelper with one static Copy method. I use Type.GetProperties to get the non-static, public properties with getters and setters. If the name and type match, I use the GetValue and SetValue methods on the PropertyInfo class to copy the value across from one object to the next. This is the result;

#region Copyright © Alteridem Consulting 2008
//
// All rights are reserved. Reproduction or transmission in whole or in part, in
// any form or by any means, electronic, mechanical or otherwise, is prohibited
// without the prior written consent of the copyright owner.
//
// Filename: CopyHelper.cs
// Date:     06/06/2008 11:18 AM
// Author:   Rob Prouse
//
#endregion

#region Using Directives

using System;
using System.Collections.Generic;
using System.Reflection;

#endregion

namespace Alteridem.ModelViewHelpers
{
    public static class CopyHelper
    {
        #region Private Members

        // We are interested in non-static, public properties with getters and setters
        private const BindingFlags flags = BindingFlags.Public | BindingFlags.Instance | BindingFlags.GetProperty | BindingFlags.SetProperty;

        #endregion

        /// <summary>
        /// Copies all public properties from one object to another.
        /// </summary>
        /// <param name="fromType">The type of the from object, preferably an interface. We could infer this using reflection, but this allows us to contrain the copy to an interface.</param>
        /// <param name="from">The object to copy from</param>
        /// <param name="toType">The type of the to object, preferably an interface. We could infer this using reflection, but this allows us to contrain the copy to an interface.</param>
        /// <param name="to">The object to copy to</param>
        public static void Copy( Type fromType, object from, Type toType, object to )
        {
            if ( fromType == null )
                throw new ArgumentNullException( "fromType", "The type that you are copying from cannot be null" );

            if ( from == null )
                throw new ArgumentNullException( "from", "The object you are copying from cannot be null" );

            if ( toType == null )
                throw new ArgumentNullException( "toType", "The type that you are copying to cannot be null" );

            if ( to == null )
                throw new ArgumentNullException( "to", "The object you are copying to cannot be null" );

            // Don't copy if they are the same object
            if ( !ReferenceEquals( from, to ) )
            {
                // Get all of the public properties in the toType with getters and setters
                Dictionary<string, PropertyInfo> toProperties = new Dictionary<string, PropertyInfo>();
                PropertyInfo[] properties = toType.GetProperties( flags );
                foreach ( PropertyInfo property in properties )
                {
                    toProperties.Add( property.Name, property );
                }

                // Now get all of the public properties in the fromType with getters and setters
                properties = fromType.GetProperties( flags );
                foreach ( PropertyInfo fromProperty in properties )
                {
                    // If a property matches in name and type, copy across
                    if ( toProperties.ContainsKey( fromProperty.Name ) )
                    {
                        PropertyInfo toProperty = toProperties[fromProperty.Name];
                        if ( toProperty.PropertyType == fromProperty.PropertyType )
                        {
                            object value = fromProperty.GetValue( from, null );
                            toProperty.SetValue( to, value, null );
                        }
                    }
                }
            }
        }
    }
}

Using this class, you can now write code like in line 2 of the second listing above. In my next post, I am going to extend this code using generics and give it a fluent interface for better readability.

I am very interested in hearing your feedback on this, so be sure to post to the comments. Do you think this is a good idea? Do you have suggestions for improvements? Let me know.

If you haven’t written a macro before, here are the steps.

1. In Visual Studio, go to Tools | Macros | Macros IDE. A new window should open and in the Project Explorer, the MyMacros project should be open.
2. Right click on the MyMacros project and select Add | Add Module. Name it CppUtilities.  The CppUtilities should open in the editor window.
3. Add the code from below into the module and save the project.

‘=====================================================================
‘ If the currently open document is a CPP or an H file, attempts to
‘ switch between the CPP and the H file.
‘=====================================================================
Public Sub SwitchBetweenSourceAndHeader()
  Dim currentDocument As String
  Dim targetDocument As String

  currentDocument = ActiveDocument.FullName

  If currentDocument.EndsWith(“.cpp”, StringComparison.InvariantCultureIgnoreCase) Then
    targetDocument = Left(currentDocument, Len(currentDocument) - 3) + “h”
    OpenDocument(targetDocument)
  ElseIf currentDocument.EndsWith(“.h”, StringComparison.InvariantCultureIgnoreCase) Then
    targetDocument = Left(currentDocument, Len(currentDocument) - 1) + “cpp”
    OpenDocument(targetDocument)
  End If

End Sub

‘=====================================================================
‘ Given a document name, attempts to activate it if it is already open,
‘ otherwise attempts to open it.
‘=====================================================================
Private Sub OpenDocument(ByRef documentName As String)
  Dim document As EnvDTE.Document
  Dim activatedTarget As Boolean
  activatedTarget = False

  For Each document In Application.Documents
    If document.FullName = documentName And document.Windows.Count > 0 Then
      document.Activate()
      activatedTarget = True
      Exit For
    End If
  Next
  If Not activatedTarget Then
    Application.Documents.Open(documentName, “Text”)
  End If
End Sub

If you switch back to Visual Studio and open the Macro Explorer, you should see the new module CppUtilities and the new macro SwitchBetweenSourceAndHeader in the tree.  You could run the macro from here, but it is much easier to bind it to a keystroke.

1. Click on Tools | Options then go to the Environment | Keyboard tab.
2. In the Show commands containing: box, type CppUtilities. This should filter the list down to one entry, Macros.MyMacros.CppUtilitities.SwitchBetweenSourceAndHeader.
3. Click on the Press shortcut keys: text box and then press the keystroke you would like to use to run the macro. If the keystroke is already used, it will show you below in the Shortcut currently used by: dropdown.  When you find one that is unused, click the Assign button to use it.  I use Ctrl+Shift+Alt+Bkspce.
4. Click OK then open a CPP or H file and give it a try.

  DateTime start = DateTime.Now;

  // Perform a long process
   Thread.Sleep( 1968 );

  DateTime end = DateTime.Now;
  TimeSpan duration = end.Subtract( start );
  Console.WriteLine( "This process took {0} ms",
    duration.TotalMilliseconds );

If you do, you should look at the System.Diagnostics.Stopwatch class that was introduced in the 2.0 framework.  You can convert the code above to the much more readable

  Stopwatch stopwatch = new Stopwatch();
  stopwatch.Start();

  // Perform a long process
  Thread.Sleep( 1968 );

  stopwatch.Stop();
  Console.WriteLine( "This process took {0} ms",
    stopwatch.ElapsedMilliseconds );

1. Click in the Find box in the toolbar,
2. Type >of followed by a space, then begin the name of the file you are looking for.
3. An auto-complete drop down will appear as you type filtering all the files in all your projects in your solution. Continue typing until the list is short enough to fine the one you want. Select it and hit enter.
4. The file will open in the editor.

Update: After this post made the front page of DotNetKicks, Aaron Lerch wrote a great post on his blog with more things that you can do with the find combo. One thing that is very useful is that with the >, you can issue any command, the alias >of mentioned here is just one of many. For a list of the commands, check out this MSDN page.

Another useful tip is that Ctrl+D or Ctrl+/ will automatically jump to the find box, so your hands don’t even need to leave your keyboard.

Update: This trick was also mentioned on Just Sayin More Words as a part of his Stupid Visual Studio Trick series. Thanks.