(.NET Core C#) Facebook Download all Photos to Local Files

Demonstrates how to download all of one's Facebook photos to a local filesystem directory. This sample code keeps a local cache to avoid re-downloading the same photos twice. The program can be run again after a time, and it will download only photos that haven't yet been downloaded.

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// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// This example will use a local disk cache to avoid re-fetching the same
// photo id after it's been fetched once.
Chilkat.Cache fbCache = new Chilkat.Cache();
// The cache will use 1 level of 256 sub-directories.
fbCache.Level = 1;
// Use a directory path that makes sense on your operating system..
fbCache.AddRoot("C:/fbCache");

// This example assumes a previously obtained an access token
Chilkat.OAuth2 oauth2 = new Chilkat.OAuth2();
oauth2.AccessToken = "FACEBOOK-ACCESS-TOKEN";

Chilkat.Rest rest = new Chilkat.Rest();

// Connect to Facebook.
bool success = rest.Connect("graph.facebook.com",443,true,true);
if (success != true) {
    Debug.WriteLine(rest.LastErrorText);
    return;
}

// Provide the authentication credentials (i.e. the access key)
rest.SetAuthOAuth2(oauth2);

// There are two choices:  
// We can choose to download the photos the person is tagged in or has uploaded
// by setting type to "tagged" or "uploaded".
rest.AddQueryParam("type","uploaded");

// To download all photos, we begin with an outer loop that iterates over
// the list of photo nodes in pages.  Each page returned contains a list of 
// photo node ids.  Each photo node id must be retrieved to get the download URL(s)
// of the actual image.

// I don't know the max limit for the number of records that can be downloaded at once.
rest.AddQueryParam("limit","100");

// Get the 1st page of photos ids.
// See https://developers.facebook.com/docs/graph-api/reference/user/photos/ for more information.
string responseJson = rest.FullRequestNoBody("GET","/v2.7/me/photos");
if (rest.LastMethodSuccess != true) {
    Debug.WriteLine(rest.LastErrorText);
    return;
}

Chilkat.JsonObject photoJson = new Chilkat.JsonObject();
Chilkat.StringArray saPhotoUrls = new Chilkat.StringArray();
Chilkat.StringBuilder sbPhotoIdPath = new Chilkat.StringBuilder();

Chilkat.JsonObject json = new Chilkat.JsonObject();
json.EmitCompact = false;
json.Load(responseJson);

int i;
string photoId;
string imageUrl;

// Get the "after" cursor.
string afterCursor = json.StringOf("paging.cursors.after");
while (json.LastMethodSuccess == true) {

    Debug.WriteLine("-------------------");
    Debug.WriteLine("afterCursor = " + afterCursor);

    // For each photo id in this page...
    i = 0;
    int numItems = json.SizeOfArray("data");
    while (i < numItems) {
        json.I = i;
        photoId = json.StringOf("data[i].id");
        Debug.WriteLine("photoId = " + photoId);

        // We need to fetch the JSON for this photo.  Check to see if it's in the local disk cache,
        // and if not, then get it from Facebook.
        string photoJsonStr = fbCache.FetchText(photoId);
        if (fbCache.LastMethodSuccess == false) {
            // It's not locally available, so get it from Facebook..
            sbPhotoIdPath.Clear();
            sbPhotoIdPath.Append("/v2.7/");
            sbPhotoIdPath.Append(photoId);

            rest.ClearAllQueryParams();
            rest.AddQueryParam("fields","id,album,images");

            Debug.WriteLine("Fetching photo node from Facebook...");

            // This REST request will continue using the existing connection.
            // If the connection was closed, it will automatically reconnect to send the request.
            photoJsonStr = rest.FullRequestNoBody("GET",sbPhotoIdPath.GetAsString());
            if (rest.LastMethodSuccess != true) {
                Debug.WriteLine(rest.LastErrorText);
                return;
            }

            // Add the photo JSON to the local cache.
            fbCache.SaveTextNoExpire(photoId,"",photoJsonStr);
        }

        // Parse the photo JSON and add the main photo download URL to saPhotoUrls
        // There may be multiple URLs in the images array, but the 1st one is the largest and main photo URL.
        // The others are smaller sizes of the same photo.
        photoJson.Load(photoJsonStr);
        imageUrl = photoJson.StringOf("images[0].source");
        if (photoJson.LastMethodSuccess == true) {

            // Actually, we'll add a small JSON document that contains both the image ID and the URL.
            Chilkat.JsonObject imgUrlJson = new Chilkat.JsonObject();
            imgUrlJson.AppendString("id",photoId);
            imgUrlJson.AppendString("url",imageUrl);
            saPhotoUrls.Append(imgUrlJson.Emit());
            Debug.WriteLine("imageUrl = " + imageUrl);
        }

        i = i + 1;
    }

    // Prepare for getting the next page of photos ids.
    // We can continue using the same REST object.
    // If already connected, we'll continue using the existing connection.
    // Otherwise, a new connection will automatically be made if needed.
    rest.ClearAllQueryParams();
    rest.AddQueryParam("type","uploaded");
    rest.AddQueryParam("limit","20");
    rest.AddQueryParam("after",afterCursor);

    // Get the next page of photo ids.
    responseJson = rest.FullRequestNoBody("GET","/v2.7/me/photos");
    if (rest.LastMethodSuccess != true) {
        Debug.WriteLine(rest.LastErrorText);
        return;
    }

    json.Load(responseJson);
    afterCursor = json.StringOf("paging.cursors.after");
}

Debug.WriteLine("No more pages of photos.");

// Now iterate over the photo URLs and download each to a file.
// We can use Chilkat HTTP.  No Facebook authorization (access token) is required to download
// the photo once the URL is known.  
Chilkat.Http http = new Chilkat.Http();

// We'll cache the image data so that if run again, we don't re-download the same image again.
int numUrls = saPhotoUrls.Count;
i = 0;
Chilkat.JsonObject urlJson = new Chilkat.JsonObject();
byte[] imageBytes = null;
Chilkat.FileAccess fac = new Chilkat.FileAccess();

while (i < numUrls) {
    urlJson.Load(saPhotoUrls.GetString(i));
    photoId = urlJson.StringOf("id");
    imageUrl = urlJson.StringOf("url");

    // Check the local cache for the image data.
    // Only download and save if not already cached.
    imageBytes = fbCache.FetchFromCache(imageUrl);
    if (fbCache.LastMethodSuccess == false) {
        //  This photo needs to be downloaded.

        Chilkat.StringBuilder sbImageUrl = new Chilkat.StringBuilder();
        sbImageUrl.Append(imageUrl);

        // Let's form a filename..
        string extension = ".jpg";
        if (sbImageUrl.Contains(".gif",false) == true) {
            extension = ".gif";
        }

        if (sbImageUrl.Contains(".png",false) == true) {
            extension = ".png";
        }

        if (sbImageUrl.Contains(".tiff",false) == true) {
            extension = ".tiff";
        }

        if (sbImageUrl.Contains(".bmp",false) == true) {
            extension = ".bmp";
        }

        Chilkat.StringBuilder sbLocalFilePath = new Chilkat.StringBuilder();
        sbLocalFilePath.Append("C:/Photos/facebook/uploaded/");
        sbLocalFilePath.Append(photoId);
        sbLocalFilePath.Append(extension);

        imageBytes = http.QuickGet(imageUrl);
        if (http.LastMethodSuccess != true) {
            Debug.WriteLine(http.LastErrorText);
            return;
        }

        // We've downloaded the photo image bytes into memory.
        // Save it to the cache AND save it to the output file.
        fbCache.SaveToCacheNoExpire(imageUrl,"",imageBytes);
        fac.WriteEntireFile(sbLocalFilePath.GetAsString(),imageBytes);

        Debug.WriteLine("Downloaded to " + sbLocalFilePath.GetAsString());
    }

    i = i + 1;
}

Debug.WriteLine("Finished downloading all Facebook photos!");