(C# UWP/WinRT) Download Binary File to In-Memory Bytes

This example demonstrates how to download the binary content of a file from Google Drive directly into local memory.

Chilkat Universal Windows Platform (UWP) / WinRT Downloads Chilkat for the Universal Windows Platform (UWP)

bool success = true;

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

// This example uses a previously obtained access token having permission for the 
// Google Drive scope.

Chilkat.AuthGoogle gAuth = new Chilkat.AuthGoogle();
gAuth.AccessToken = "GOOGLE-DRIVE-ACCESS-TOKEN";

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

// Connect using TLS.
// A single REST object, once connected, can be used for many Google Drive REST API calls.
// The auto-reconnect indicates that if the already-established HTTPS connection is closed,
// then it will be automatically re-established as needed.
bool bAutoReconnect = true;
success = await rest.ConnectAsync("www.googleapis.com",443,true,bAutoReconnect);

// Provide the authentication credentials (i.e. the access token)
rest.SetAuthGoogle(gAuth);

// ------------------------------------------------------------------------------
// To download a file, we must know the file ID.
// In a previous example (see Build Local Metadata Cache
// we built a local cache to make it easy to lookup file IDs given a file path.
// Let's say we want to download "testFolder/abc/123/penguins.jpg".
// First we lookup the fileId in the cache.  With the fileId, we can download the file.
Chilkat.Cache gdCache = new Chilkat.Cache();
gdCache.Level = 0;
gdCache.AddRoot("C:/ckCache/googleDrive");

string fileId = gdCache.FetchText("testFolder/abc/123/penguins.jpg");
if (gdCache.LastMethodSuccess != true) {
    Debug.WriteLine("Filepath not found in cache.");
    return;
}

// We need to send a GET request like this:
// GET https://www.googleapis.com/drive/v3/files/fileId?alt=media
// The fileId is part of the path.
Chilkat.StringBuilder sbPath = new Chilkat.StringBuilder();
sbPath.Append("/drive/v3/files/");
sbPath.Append(fileId);
rest.AddQueryParam("alt","media");

// To download to memory, we'll send the request in one call, then receive
// the response header, and then the response body.
// If the response header indicates failure or an unexpected response, then the
// body is not the data we desire.

// First send the HTTP request.
success = await rest.SendReqNoBodyAsync("GET",sbPath.GetAsString());
if (success != true) {
    Debug.WriteLine(rest.LastErrorText);
    return;
}

// Get the response header.
int statusCode = await rest.ReadResponseHeaderAsync();
if (statusCode != 200) {
    Debug.WriteLine("response status code = " + Convert.ToString(rest.ResponseStatusCode));
    Debug.WriteLine("response status text = " + rest.ResponseStatusText);
    Debug.WriteLine("response header: " + rest.ResponseHeader);

    // Read the response body (which should be error text or HTML)
    string errResponseBody = await rest.ReadRespBodyStringAsync();
    if (rest.LastMethodSuccess == true) {
        Debug.WriteLine("response body: " + errResponseBody);
    }

    return;
}

// Read the response body, which should contain the file data.
byte[] jpgBytes = null;
jpgBytes = await rest.ReadRespBodyBinaryAsync();
if (rest.LastMethodSuccess != true) {
    Debug.WriteLine(rest.LastErrorText);
    return;
}

// Save jpgBytes to a file so we can examine the file to verify that it worked.
Chilkat.FileAccess fac = new Chilkat.FileAccess();
fac.WriteEntireFile("qa_output/penguins_out.jpg",jpgBytes);

Debug.WriteLine("File downloaded.");