CODEWITHSUNDEEP
c#reflectiontaglib-sharp
Fill Freeman
Fill Freeman

Reputation: 199

How to use dynamically linked dll in c#

I imported the taglib-sharp dll (that had been copied to the bin/debug folder of my project) in my C# application and then used types and methods from the library in the following way:

using TagLib;

private void method()
{
    TagLib.File file = TagLib.File.Create("C:\\temp\\some.mp3");
    TagLib.Tag tag = file.GetTag(TagLib.TagTypes.Id3v2);
}

Now I want to link the dll dynamically. How can I implement the same functional in this case?

That, what I've tried:

using System.Reflection

private void method()
{
    Assembly TagLib = Assembly.Load("taglib-sharp");
        
    Type TagLibFile = TagLib.GetType("File");
    dynamic LibFile = Activator.CreateInstance(TagLibFile);
    
    TagLibFile file = LibFile.Create("c:\\temp\\some.mp3");
}

In this implementation, VisualStudio says that I can't use the tagLibFile variable as a type. I supposed that when I get a type from dll, I will be able to create variables of this type.

By the way, is this approach is correct?

P.S. Also, I tried to use the invoke method, but I was not sure what object I should pass as a first argument.

UPD

Based on @nawfal's awnser below, I've got the following working code:

using System.Reflection

private void method()
{
    Assembly TagLib = Assembly.Load("taglib-sharp");

    // get the File type
    var fileType = TagLib.GetType("TagLib.File");
    // get the overloaded File.Create method
    var createMethod = fileType.GetMethod("Create", new[] { typeof(string) });

    // get the TagTypes method that contains Id3v2 field
    Type tagTypes = TagLib.GetType("TagLib.TagTypes");
    // get the overloaded File.GetTag method
    var getTagMethod = fileType.GetMethod("GetTag", new[] {tagTypes});
    // obtain the file
    dynamic file = createMethod.Invoke(null, new[] { "C:\\temp\\some.mp3" });
    // obtain the Id3v2 field value
    FieldInfo Id3TagField = tagTypes.GetField("Id3v2");
    var Id3Tag = Id3TagField.GetValue(tagTypes);

    // obtain the actual tag of the file
    var tag = getTagMethod.Invoke(file, new[] { Id3Tag });
}

Upvotes: 2

Views: 370

Answers (2)

nawfal
nawfal

Reputation: 73233

You should be doing something like this: 

private void method()
{
    var assembly = Assembly.Load("taglib");
    var type = assembly.GetType("namespace.File"); // namespace qualified class name
    // assuming you only have one Create method, otherwise use reflection to resolve overloads
    var method = type.GetMethod("Create");

    dynamic file = method.Invoke(null, new[] { "C:\\temp\\some.mp3" }); // null for static methods
    var tag = file.GetTag(TagLib.TagTypes.Id3v2); // not sure if you can pass those params, 
                                                  // may be do reflection to get them too
}

Kindly rethink if you want it to be dynamic. If you can reference the dll then you can still get the benefits of strong typing.

Upvotes: 1

Chilli
Chilli

Reputation: 337

Save it as object.

object file = LibFile.Create(fi.FullName);

Should work.

Dynamic loading dlls works much different.

Upvotes: 0

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