A Faster Way to Add Image Assets to Your Xamarin.iOS Project in Visual Studio 2017

While Visual Studio has an editor that can help to add new image assets to a project, it is pretty slow when adding a bunch of new images. If you have to add a lot of images to add, it even crashes once in while, which can be annoying. Because I was in the process of adding more than a hundred images for porting my first app ever from a Windows Phone to iOS and Android, I searched for a faster way — and found it.

What's Going on Under the Hood?

When you add an imageset to your assets structure, Visual Studio does quite some work. These are the steps that are done:

1. Creation of a folder for the imageset in the Assets folder.
2. Creation of a Contents.jsonfile.
3. Modification of the Contents.json file.
4. Modification of the .csproj file.

This takes some time for every image, and Visual Studio seems to be quite busy with these steps. After analyzing the way imagesets get added, I immediately recognized that I am faster than Visual Studio if I do that work manually.

How to Add the Assets: Step-by-Step

1. Right click on the project in Solution Explorer and select 'Open Folder in File Explorer' and find the 'Assets' folder.
2. Create a new folder in this format: '[yourassetname].imageset'.
3. Add your image to the folder.
4. Create a new file with the name Contents.json
5. Open the file (I use Notepad++ for such operations) and add this minimum required jsonto it:

   {
     "images": [
       {
         "scale": "1x",
         "idiom": "universal",
         "filename": "[yourimage].png"
       },
       {
         "scale": "2x",
         "idiom": "universal",
         "filename": "[yourimage].png"
       },
       {
         "scale": "3x",
         "idiom": "universal",
         "filename": "[yourimage].png"
       },
       {
         "idiom": "universal"
       }
     ],
     "properties": {
       "template-rendering-intent": ""
     },
     "info": {
       "version": 1,
       "author": ""
     }
   }

6. Go back to Visual Studio, right click on the project again and select 'Unload Project'.
7. Right click again and select 'Edit [yourprojectname].iOS.csproj'.
8. Find the ItemGroup with the Assets.
9. Inside the ItemGroup, add your imageset with these two entries:

   <ImageAsset Include="Assets.xcassets\[yourassetname].imageset\[yourimage].png">
     <Visible>false</Visible>
   </ImageAsset>
   <ImageAsset Include="Assets.xcassets\[yourassetname].imageset\Contents.json">
     <Visible>false</Visible>
   </ImageAsset>   

10. Close the file and reload the project by selecting it from the context menu in Solution Explorer.

If you followed this steps, your assets should be visible immediately:

I did not measure the time exactly, but I felt I was significantly faster by adding all those images that way. Your mileage may vary, depending on the power of your dev machine.

Conclusion

Features like the AssetManager for iOS in Visual Studio are nice to have, but some have some serious performance problems (most of them are already known). By taking over the process manually, one can be a lot faster than a built-in feature. That said, like always, I hope this post is helpful for some of you.

Happy coding, everyone!