创建实现Interface的每种类型的对象

Question

In my program, I use a number of sources to obtain data. The actual implementation does not really matter, but they all implement a "Source" interface which has a call to fetch data given a particular input.

When I need data, I want to call all the sources one at a time and do something with the data.

Currently I do this:

List<Source> sources = new List<Source>()
sources.Add(new SourceA());
sources.Add(new SourceB());
//...

//----

foreach (Source source in sources)
{
string data = source.getData(input);
//do something with the data
}

The issue is that I need to hard-code the insertion of the sources into the list. Is there a way (using reflection perhaps) of automating the process? I'd like the list to contain all objects which implement the 'Source' interface - without having to hard-code it myself.

Answer 1

You can use reflection to search the assemblies for classes that implement your interface and create instances. I would consider renaming to ISource unless there is shared code in the base class.

foreach (var type in Assembly.GetExecutingAssembly().GetTypes())
{
    if (typeof(ISource).IsAssignableFrom(type))
    {
        sources.Add((ISource)Activator.CreateInstance(type));
    }
}

Answer 2

Here is some code I use to load Addons stored in an external assembly. The bit towards the bottom shows how to get all types with a certain Interface called 'IWAPAddon' this is the part of code you can use:

//If the plugin assembly is not aleady loaded, load it manually
if ( PluginAssembly == null )
{
    PluginAssembly = Assembly.LoadFile( oFileInfo.FullName );
}

if ( PluginAssembly != null )
{
    //Step through each module
    foreach ( Module oModule in PluginAssembly.GetModules() )
    {
        //step through the types in each module
        foreach ( Type oModuleType in oModule.GetTypes() )
        {
            foreach ( Type oInterfaceType in oModuleType.GetInterfaces() )
            {
                if ( oInterfaceType.Name == "IWAPAddon" )
                {
                    this.Addons.Add( oModuleType );
                }
            }
        }
    }
}

Answer 3

Based on Slugart's suggestion:

foreach (var type in Assembly.GetExecutingAssembly().GetTypes())
            {
                if (type.GetInterfaces().Contains(typeof(ISource)) && type.IsInterface == false
                {
                    sources.Add((ISource)Activator.CreateInstance(type));
                }
            }