ProviderHostedApp - CopyDocument

CopyDocument.cs

string filePath = "/TestLibrary/TestDocument.pptx";
var spContext = SharePointContextProvider.Current.GetSharePointContext(HttpContext);

using (var sourceContext = spContext.CreateUserClientContextForSPHost())
{
    Microsoft.SharePoint.Client.File sourceFile = sourceContext.Web.GetFileByServerRelativeUrl(filePath);
    //file stream will be used to upload in destination library
    var fileStream = sourceFile.OpenBinaryStream();
    sourceContext.Load(sourceFile, k => k.ServerRelativeUrl, k => k.Name);
    sourceContext.ExecuteQuery();

    //generate destination context
    string destinationSiteUrl = "url_of_destination_sharepoint_site"; //I used mysite url here
    Uri destinationSiteUri = new Uri(destinationSiteUrl);

    //target realm of the tenant (This is constant per tenant)
    string targetRealm = TokenHelper.GetRealmFromTargetUrl(destinationSiteUri);

    //generate access token for destination site
    string accessToken = TokenHelper.GetAppOnlyAccessToken(TokenHelper.SharePointPrincipal, destinationSiteUri.Authority, targetRealm).AccessToken;
    //get destination site context using access token
    using (var destinationContext = TokenHelper.GetClientContextWithAccessToken(destinationSiteUrl, accessToken))
    {
        //load server relative url of destination library
        var destinationLibrary = destinationContext.Web.Lists.GetByTitle("DestinationLibrary");

        FileCreationInformation fileCreationInfo = new FileCreationInformation();
        fileCreationInfo.ContentStream = fileStream.Value;
        fileCreationInfo.Url = sourceFile.Name;
        fileCreationInfo.Overwrite = false;
        Microsoft.SharePoint.Client.File destinationFile = destinationLibrary.RootFolder.Files.Add(fileCreationInfo);
        destinationContext.Load(destinationFile, k => k.ServerRelativeUrl);
        destinationContext.ExecuteQuery();
    }
}