Ken Kopczyk

Hurdles in .NET Development

Archive for the ‘.NET SDK’ Category

Persisting User Settings Using Serialization

Posted by Ken on January 31, 2010

Recently, I was faced with the task of implementing custom user settings that were to be saved between sessions. My solution was to save these settings to a file during application tear down and to load the file as part of the application’s startup. To accomplish this, I used the following steps:

  1. Create an XML schema definition file (xsd) to define the data being stored.
  2. Create a Serializable class based on the xsd so the data may be instantiated/accessed in the code.
  3. Use serialization and deserialization to load and unload the user settings.

Using xsd.exe to generate a serializable class.
The first step I took was to create an XML schema definition file to represent my user settings data.  Once the schema was finished, I used the XML Schema Definition Tool (xsd.exe) to generate a serializable class from the schema.  This executable is part of the .NET SDK and is a real time saver. Use the following command line parameters to generate a serializable class based on an xsd file:

xsd.exe -c -l:c# -n:[namespace for the generated class] [XML Schema Definition File]

Example:

xsd.exe -c -l:c# -n:MyProgram.Utilities MyUserSettings.xsd

This example will create a serializable class called MyUserSettings.cs.

Serialization and Deserialization
Simply stated, serialization is the process of converting an object instance into a stream of bytes, text, XML or other formats so that it can be persisted into storage medium or transfered across a network. Deserialization is the opposite process which converts the persisted data back into an object instance. The following are sample methods for each process:

using System;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
using System.Text;
using System.Xml;
using System.Xml.Serialization;

namespace MyProgram.Utilities
{
    public static class Serialization
    {
        public enum SerializationMethod { Binary, XML };

        public static void Serialize(string sFilePath, Type type, object objectToSerialize, SerializationMethod serializationMethod)
        {
            if (!File.Exists(sFilePath))
            {
                return;
            }

            Stream writeStream = null;
            XmlTextWriter xtw = null;
            try
            {
                writeStream = File.Open(sFilePath, FileMode.Truncate);
                if (serializationMethod == SerializationMethod.XML)
                {
                    XmlSerializer xs = new XmlSerializer(type);
                    xtw = new XmlTextWriter(writeStream, null);
                    xs.Serialize(xtw, objectToSerialize);
                }
                else if (serializationMethod == SerializationMethod.Binary)
                {
                    new BinaryFormatter().Serialize(writeStream, objectToSerialize);
                }
            }
            finally
            {
                if (xtw != null)
                {
                    xtw.Close();
                }
                if (writeStream != null)
                {
                    writeStream.Close();
                    writeStream.Dispose();
                }
            }
        }

        public static object Deserialize(string sFilePath, Type type, SerializationMethod serializationMethod)
        {
            if (!File.Exists(sFilePath))
            {
                return Activator.CreateInstance(type);
            }

            Stream stream = null;
            object deserializedObject = null;
            try
            {
                stream = File.OpenRead(sFilePath);
                if (serializationMethod == SerializationMethod.XML)
                {
                    XmlSerializer xmlSerializer = new XmlSerializer(type);
                    deserializedObject = xmlSerializer.Deserialize(stream);
                }
                else if (serializationMethod == SerializationMethod.Binary)
                {
                    deserializedObject = new BinaryFormatter().Deserialize(stream);
                }
            }
            finally
            {
                if (stream != null)
                {
                    stream.Close();
                    stream.Dispose();
                }
            }
            return deserializedObject;
        }
    }
}

Note that these methods support both XML (human readable) and binary (gibberish) de/serialization. This comes in handy if you want to prevent the settings files from being tampered with in a production environment, but you’d prefer them easier to work with during development. Using preprocessor directives, you can do something like the following to make the files human readable at development time, but garbled when they are released into the wild:

MyUserSettings userSettings = GetMySettings();
#if DEBUG
Serialization.SerializationMethod serializationMethod = Serialization.SerializationMethod.XML;
#else
Serialization.SerializationMethod serializationMethod = Serialization.SerializationMethod.Binary;
#endif
Serialization.Serialize(sFullSettingsFileName, typeof(MyUserSettings), userSettings, serializationMethod);
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Creating COM Interop Assemblies with .NET 2.0

Posted by Ken on August 18, 2009

If you work with .NET long enough, sooner or later you’ll probably need to leverage older Win32 COM components. To allow the CLR managed code of .NET to communicate with the unmanaged code of COM, a “middleman” in the form of an interop assembly must be created. This can be done via Visual Studio or the Type Library Importer.

Creating an interop assembly with Visual Studio
Enter the “Add reference” dialog of your project, browse for your registered COM server and select it. Now take a look at the properties of the newly created reference. It is actually pointing to a new assembly called Interop.COMServerName.dll: If your COM server is foo.dll, the resulting assembly is called Interop.foo.dll. You will find this assembly in your bin directory after you build.

If your project uses an .snk or .pfx for strong naming, the interop assembly will also be strong named using that file.

A major limitation of this method I found was the fact that you can’t change the version number of the interop assembly. It is always 1.0.0.0. Bummer.

Creating an interop assembly with Type Library Importer
If you need more control, then you should use the Type Library Importer (tlbimp). This application is included with the .NET SDK.

Running the following command will create an interop assembly with a version number of your choosing:
Using our foo.dll example:

tlbimp foo.dll /out:Interop.foo.dll /asmversion:2.0.0.0

If you need the interop assembly strongly named, you can do that also. If you are using an .snk, use the following:

tlbimp foo.dll /out:Interop.foo.dll /asmversion:2.0.0.0 /keyfile:MyKey.snk

If you are using a .pfx for strong naming, it’s a bit trickier. You will also need to leverage the Strong Name Tool (sn) to create a keycontainer:

echo Prompts you for .pfx password
sn -i MyKey.pfx KeyContainerName

tlbimp foo.dll /out:Interop.foo.dll /asmversion:2.0.0.0 /keycontainer:KeyContainerName

echo Housecleaning.  Removes the key container from memory.
sn -d KeyContainerName

Now add it as a reference and you’re good to go!

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