First, we need to make sure that our project has a settings file. It is usually under the Properties node of the project. If it is not, right click on the solution and Add | New Item… | Visual C# Items | General | Settings File and name it Settings.settings. Next, drag it and drop it in your project’s Properties folder.

Next, you need to add a bool User setting called UpgradeRequired and default it to true. Next, at the very beginning of your Main, you check if UpgradeRequired is true, and if it is, upgrade the settings, set UpgradeRequired to false and save out the settings. This will pull in the settings from previous versions of your application.

Your settings should look like this,

The code should look like this,

static void Main( string[] args )
{
   // Upgrade settings if required
   if ( Properties.Settings.Default.UpgradeRequired )
   {
      Properties.Settings.Default.Upgrade();
      Properties.Settings.Default.UpgradeRequired = false;
      Properties.Settings.Default.Save();
   }

   // Do work...

   // At the end of main, save out any changes to settings
   Properties.Settings.Default.Save();
}

Now you just need to create new settings and use them in your application. Any setting with Application scope will be set in your app.config and will be read-only. This is often used for connection strings and other information that is unlikely to change. User scoped settings also have their default values in app.config, but any changes are written out to an XML file in the user’s AppData folder.

Also, notice that code gets generated for any setting that you create and you access it through a property on Properties.Settings.Default. You can use any complex type for a setting, including classes in your application, as long as they are Serializable.

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.

It took a fair amount of searching and code tweaking, but I finally worked it all out.

1. Add a reference to the COM Microsoft Windows Installer Object Library.
2. Add a using WindowsInstaller;
3. Add the following static method to your code (error checking removed for brevity.)

public static string GetMsiProperty( string msiFile, string property )
{
   string retVal = string.Empty;

   // Create an Installer instance
   Type classType = Type.GetTypeFromProgID( “WindowsInstaller.Installer” );
   Object installerObj = Activator.CreateInstance( classType );
   Installer installer = installerObj as Installer;

   // Open the msi file for reading
   // 0 - Read, 1 - Read/Write
   Database database = installer.OpenDatabase( msiFile, 0 );

   // Fetch the requested property
   string sql = String.Format(
      “SELECT Value FROM Property WHERE Property=’{0}’”, property );
   View view = database.OpenView( sql );
   view.Execute( null );

   // Read in the fetched record
   Record record = view.Fetch();
   if ( record != null )
      retVal = record.get_StringData( 1 );

   return retVal;
}

If you want to look up the version, just pass in the name of the MSI file you want to inspect and “ProductVersion” for the property you want to return. For example;

string version = GetMsiProperty( msiFile, “ProductVersion” );

You can use this method to look up other properties in the installer. Some common ones you might want are ProductName, ProductCode, UpgradeCode, Manufacturer, ARPHELPLINK, ARPCOMMENTS, ARPCONTACT, ARPURLINFOABOUT and ARPURLUDATEINFO. For a full list of properties, see the MSDN Reference, but remember that most of the properties listed on that page are only for already installed applications and won’t be included in the installer.

If you find this code useful or the code is not self-explanatory, please leave a comment.