# Developer's Guide: .NET

**Important**: This is an old version of this page. For the latest version, use the links in the left-side navbar.

The Blogger Data API allows client applications to view and update Blogger
content in the form of Google Data API feeds.

Your client application can use the Blogger Data API to create new blog
posts, edit or delete existing blog posts, and query for blog posts that match
particular criteria.

In addition to providing some background on the capabilities of the Blogger
Data API, this document provides examples of basic Data API interactions using
the [.NET client library](https://code.google.com/p/google-gdata/). If
you're interested in understanding more about the underlying protocol that the
library uses, see the [Protocol section](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol) of
this developer's guide.

## Contents

1. [Audience](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#Audience)
2. [Getting started](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#GettingStarted)
   1. [Creating a Blogger account](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#CreatingAccount)
   2. [Running the sample code](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#RunningSamples)
3. [Authenticating to the Blogger service](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#Authenticating)
   1. [AuthSub proxy authentication](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#AuthSub)
   2. [ClientLogin username/password authentication](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#ClientLogin)
4. [Retrieving a list of blogs](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#RetrievingMetafeed)
5. [Creating posts](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#CreatingEntries)
   1. [Publishing a blog post](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#CreatingPublicEntries)
   2. [Creating a draft blog post](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#CreatingDraftEntries)
6. [Retrieving posts](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#RetrievingEntries)
   1. [Retrieving all blog posts](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#RetrievingWithoutQuery)
   2. [Retrieving posts using query parameters](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#RetrievingWithQuery)
7. [Updating posts](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#UpdatingEntries)
8. [Deleting posts](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#DeletingEntries)
9. [Comments](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#Comments)
   1. [Creating comments](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#CreatingComments)
   2. [Retrieving comments](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#RetrievingComments)
   3. [Deleting comments](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#DeletingComments)

## Audience

This document is intended for programmers who want to write .NET client
applications that can interact with Blogger.

This document assumes that you understand the general ideas behind the [Google Data APIs
protocol](https://developers.google.com/gdata/docs/2.0/basics).

For reference information about the classes and methods provided by the
client library, see the [.NET client
library API reference](http://google-gdata.googlecode.com/svn/docs/Index.html). For general Blogger Data API reference
information, see the [Protocol reference
guide](https://developers.google.com/blogger/docs/1.0/reference).

## Getting started

For help setting up the client library, see the [Getting
Started Guide](https://developers.google.com/gdata/articles/dotnet_client_lib).

To use the .NET client library, you'll need the .NET 1.1 runtime, and you
should also be current on all patches. After [downloading the
client library](https://code.google.com/p/google-gdata/downloads/list), you'll find the DLLs you need to get started in the
`lib/Release` subdirectory of the distribution.

### Creating a Blogger account

You may want to [sign up for a
Blogger account](http://www.blogger.com/signup.g) for testing purposes. Blogger uses [Google Accounts](https://www.google.com/accounts/Login), so if you
already have a Google account, you're all set.

### Running the sample code

A full working sample client, containing all the sample code shown in this
document, is available in the .NET client library project. The sample is located
at [/trunk/clients/cs/samples/blogger/ConsoleSample.cs](http://google-gdata.googlecode.com/svn/trunk/clients/cs/samples/blogger/ConsoleSample.cs)
in the Source tab of the SVN repository.

Before compiling and running this sample, update the values of
`username`, `password`, `blogName`, and
`postId` with the appropriate values. The `username` and
`password` values represent the credentials used to log in to
Blogger. The `blogName` value is the start of your blog's blogspot
URL.

The sample client performs several operations on the provided blog to
demonstrate the use of the Blogger Data API.

To compile the examples in this document into your own code, you'll need the
following `using` statements:

```
using Google.GData.Client;
using System.Net;
using System.Xml;
using System.Text.RegularExpressions;
```

## Authenticating to the Blogger service

You can access both public and private feeds using the Blogger Data API.
Public feeds don't require any authentication, but they are read-only. If you
want to modify blogs, then your client needs to authenticate before requesting
private feeds. It can authenticate using either of two approaches: [AuthSub](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#AuthSub) proxy authentication or [ClientLogin](https://developers.google.com/blogger/docs/1.0/developers_guide_dotnet#ClientLogin) username/password authentication.

For more information about authentication with Google Data APIs in general,
see the [authentication documentation](https://developers.google.com/gdata/docs/auth/overview).

### AuthSub proxy authentication

AuthSub proxy authentication is used by web applications that need to
authenticate their users to Google Accounts. The website operator and the client
code don't have access to the username and password for the Blogger user;
instead, the client obtains special AuthSub tokens that allow the client to act
on a particular user's behalf. For more detailed information, see the [AuthSub documentation](https://developers.google.com/accounts/docs/AuthSub).

When a user first visits your application, they have not yet been
authenticated. In this case, you need to display some information and a link
directing the user to a Google page to authenticate your request for access to
their blogs.

Suppose the following ASP hyperlink is defined in your page:

```
<asp:HyperLink ID="GotoAuthSubLink" runat="server"/>
```

Then to construct the AuthSubRequest URL for your application, make a .NET
client library call as follows:

```
GotoAuthSubLink.Text = "Login to your Google Account";
GotoAuthSubLink.NavigateUrl =
  AuthSubUtil.getRequestUrl("http://www.example.com/RetrieveToken",
  "http://www.blogger.com/feeds/",
  false,
  true);
```

The `getRequestUrl` method takes the following parameters
(corresponding to the query parameters used by the AuthSubRequest handler):

next
:   The URL of the page that Google should redirect the user to after authentication.

scope
:   Indicates that the application is requesting a token to access Blogger
    feeds. The scope string to use is `http://www.blogger.com/feeds/`
    (URL-encoded, of course).

secure
:   Indicates whether the client is requesting a secure token.

session
:   Indicates whether the token returned can be exchanged for a multi-use (session) token.

The above example shows a call that doesn't request a secure token (the value
of `secure` is `false`). The resulting request URL might
look like this:

```
https://www.google.com/accounts/AuthSubRequest?scope=http%3A%2F%2Fwww.blogger.com%2Ffeeds%2F&session=1&secure=0&next=http%3A%2F%2Fwww.example.com%2FRetrieveToken
```

The user follows the link to Google's site and authenticates to their Google Account.

After the user authenticates, the AuthSub system redirects them to the URL
you specified in the `next` query parameter of the AuthSubRequest
URL. The AuthSub system appends an authentication token to that URL, as the
value of the `token` query parameter. Therefore, the token is
accessible as a variable in the ASP page's `Request.QueryString`
object. The user is redirected to a URL that looks like this:

```
http://www.example.com/RetrieveToken?token=yourAuthToken
```

This token value represents a single-use AuthSub token. In this example,
since `session = true` was specified, this token can be exchanged for
an AuthSub session token, as follows:

```
SessionsessionToken = AuthSubUtil.exchangeForSessionToken(Request.QueryStringtoken, null);
```

That is, you pass your one-time-use token to the
`exchangeForSessionToken` method, along with either `null`
(for unregistered mode) or a private key (for registered mode), and the AuthSub
interface returns a session token. For more information about registered
applications and private keys, see the "[Signing requests](https://developers.google.com/accounts/docs/AuthSub#signingrequests)"
section of the AuthSub documentation.

Your application can then use the session token value in subsequent
interactions with Blogger. To tell the .NET client library to automatically send
the Authorization header (containing the session token) with each request, do
the following:

```
GAuthSubRequestFactory authFactory = new GAuthSubRequestFactory("blogger", "BloggerSampleApp");
authFactory.Token = SessionsessionToken.ToString();
Service service = new Service(authFactory.ApplicationName);
service.RequestFactory = authFactory;
```

### ClientLogin username/password authentication

Use ClientLogin authentication if your client is a standalone, single-user
"installed" client (such as a desktop application). Set the
credentials of your service object as follows:

```
Service service = new Service("blogger", "exampleCo-exampleApp-1");
service.Credentials = new GDataCredentials("user@example.com", "secretPassword");
GDataGAuthRequestFactory factory = (GDataGAuthRequestFactory) service.RequestFactory;
factory.AccountType = "GOOGLE";
```

In the snippet above, we pass two parameters to the `Service`
constructor. The first parameter is the name of the service we want to interact
with. The second parameter is the name of our application in the form
<var translate="no">companyName</var>-<var translate="no">applicationName</var>-<var translate="no">versionID</var>. We also
set the `Service.RequestFactory` to only use a `GOOGLE`
account type in order to allow proper authentication for [G Suite](http://www.google.com/a/) users.

For more information about ClientLogin authentication, including sample
requests and responses, see the [Authentication for Installed
Applications](https://developers.google.com/accounts/docs/AuthForInstalledApps) documentation.

**Note**: Use the same token for all requests in a
given session; don't acquire a new token for each Blogger request.

**Note** : As described in the ClientLogin
documentation, the authentication request may fail and request a CAPTCHA
challenge. If you want Google to issue and handle the CAPTCHA challenge, then
send the user to
`https://www.google.com/accounts/DisplayUnlockCaptcha?service=blogger`
(rather than to the CAPTCHA-handling URL given in the ClientLogin
documentation).

## Retrieving a list of blogs

The Blogger Data API provides a feed that lists the blogs for a particular
user; that feed is known as a "metafeed."

The following sample code uses an authenticated `Service` object
to retrieve the metafeed and then prints each blog's title.

```
query.Uri = new Uri("http://www.blogger.com/feeds/default/blogs");
AtomFeed feed = null;
try
{
  feed = service.Query(query);
  foreach (AtomEntry entry in feed.Entries)
  {
    Console.WriteLine("Blog Title: " + entry.Title.Text);
  }
}
```

Note the URL used by the `getFeed` method. This is the default
metafeed URL; it returns a list of blogs for the currently authenticated user.
To access a feed for a different user, you can put the user's ID in place of
`default` in the metafeed URL. The user's ID is the string of digits
at the end of the user's profile URL.

## Creating posts

The Blogger Data API allows you to create and publish new blog entries, as
well as creating drafts of entries.

All of the following samples assume you have an authenticated
`Service` object.

**Note**: Setting a custom author for posts is
currently not supported. All new posts will appear as if they were created by
the currently authenticated user.

### Publishing a blog post

You can use the .NET client library to publish new blog entries.

First, create an `AtomEntry` object to represent the blog post.
Then you can set the title, content and other attributes of the blog post.
Finally, use the `Service` object to insert the post. Here's an
example of how to publish a new blog post:

```
AtomEntry newPost = new AtomEntry();
newPost.Title.Text = "Marriage!";
newPost.Content = new AtomContent();
newPost.Content.Content = "<div xmlns='http://www.w3.org/1999/xhtml'>" +
  "<p>Mr. Darcy has <em>proposed marriage</em> to me!</p>" +
  "<p>He is the last man on earth I would ever desire to marry.</p>" +
  "<p>Whatever shall I do?</p>" +
  "</div>";
newPost.Content.Type = "xhtml";

Uri blogFeedUri = new Uri("http://www.blogger.com/feeds/" + blogId + "/posts/default");
AtomEntry createdEntry = service.Insert(blogFeedUri, newPost);
```

The `Insert` method takes the service's post URL as a parameter.
Then the method returns the entry as it was stored by Blogger. The entry
returned is the same one you sent, but it also contains various elements added
by Blogger, such as a post ID.

If your request fails for some reason, Blogger may return a different status
code. For information about the status codes, see the [Google Data API protocol reference document](https://developers.google.com/gdata/docs/2.0/reference).

### Creating a draft blog post

Draft posts are created in the same way as public posts, but you need to set
the `draft` attribute of the `AtomEntry` object. The blog
post above could be created as a draft by adding the highlighted line:

```
AtomEntry newPost = new AtomEntry();
newPost.Title.Text = "Marriage!";
newPost.Content = new AtomContent();
newPost.Content.Content = "<div xmlns='http://www.w3.org/1999/xhtml'>" +
    "<p>Mr. Darcy has <em>proposed marriage</em> to me!</p>" +
    "<p>He is the last man on earth I would ever desire to marry.</p>" +
    "<p>Whatever shall I do?</p>" +
    "</div>";
newPost.Content.Type = "xhtml";
newPost.IsDraft = true;

Uri blogFeedUri = new Uri("http://www.blogger.com/feeds/" + blogId + "/posts/default");
AtomEntry createdEntry = service.Insert(blogFeedUri, newPost);
```

You can turn an existing draft blog post into a published post by retrieving
the draft post, setting the draft attribute to false, and then updating the
post. We'll cover retrieving and updating posts in the next two sections.

## Retrieving posts

The following sections describe how to retrieve a list of blog posts, with
and without query parameters.

You can query a Blogger public feed without authentication. Therefore, you
don't need to set credentials or do AuthSub authentication before retrieving
posts from a public blog.

### Retrieving all blog posts

To retrieve the user's posts, call the same `getFeed` method used
to retrieve the blogs metafeed, but this time send the blog-post feed URL:

```
query.Uri = new Uri("http://www.blogger.com/feeds/" + blogId + "/posts/default");
feed = service.Query(query);
Console.WriteLine(feed.Title.Text);
foreach (AtomEntry entry in feed.Entries)
{
  Console.WriteLine("Entry Title: " + entry.Title.Text);
}
```

### Retrieving posts using query parameters

The Blogger Data API lets you request a set of entries that match specified
criteria, such as requesting blog posts published or updated in a given date
range. To do this, you create a `FeedQuery` object and pass it to the
`Service.Query()` method.

For example, to send a date-range query, set the `MinPublication`
and `MaxPublication` members of the `FeedQuery` object.
The following code snippet prints the title of each blog post published between
the given start time and end time:

```
FeedQuery query = new FeedQuery();
query.Uri = new Uri("http://www.blogger.com/feeds/" + blogId + "/posts/default");
query.MinPublication = new DateTime(2006, 1, 1);
query.MaxPublication = new DateTime(2007, 4, 12);
AtomFeed feed = service.Query(query);
foreach (AtomEntry entry in feed.Entries)
{
  Console.WriteLine("  Entry Title: " + entry.Title.Text);
}
```

Notice that the `FeedQuery` object is constructed using the same post feed URL used to retrieve posts.

The Blogger Data API supports the following query parameters:

alt
:   The type of feed to return, such as `atom` (the default) or `rss`.

<var translate="no">/category</var>
:   Specify categories (also known as labels) to filter the feed results. For example, `http://www.blogger.com/feeds/blogID/posts/default/-/Fritz/Laurie` returns entries with both the labels `Fritz` and `Laurie`.

max-results
:   The maximum number of entries to return.

orderby
:   The order in which to return entries, such as `lastmodified` (the default), `starttime`, or `updated`.

published-min, published-max
:   The bounds on entry publication dates.

start-index
:   The 1-based index of the first result to be retrieved (for paging).

updated-min, updated-max
:   The bounds on entry update dates. These query parameters are ignored unless the `orderby` parameter is set to `updated`.

For more information about query parameters, see the [Blogger Data API Reference
Guide](https://developers.google.com/blogger/docs/1.0/reference#Parameters) and the [Google
Data APIs Reference Guide](https://developers.google.com/gdata/docs/2.0/reference#Queries).

## Updating posts

To update an existing blog post, first you retrieve the entry you want to
update, then you modify it, and then you send it to Blogger using the entry's
`Update()` method. The following code snippet modifies the title of a
blog entry, assuming that you've already retrieved the entry from the
server.

```
static AtomEntry EditEntry(AtomEntry toEdit)
{
  // Edit the entry by changing the Title and calling Update().
  if (toEdit != null)
  {
    toEdit.Title.Text = "Marriage Woes!";
    toEdit = toEdit.Update();
  }
  return toEdit;
}
```

The above code returns an `AtomEntry` containing the entire
newly-updated post. To update any other properties, simply set them in the
`AtomEntry` object before calling `Update()`.

**Note**: Modifying the author data associated with
posts is currently not supported.

## Deleting posts

To delete a post, call the `Delete` method on an existing
`AtomEntry` object, like this:

```
static void DeleteEntry(AtomEntry toDelete)
{
  // Delete the edited entry
  if (toDelete != null)
  {
    toDelete.Delete();
  }
}
```

## Comments

The Blogger Data API allows for creating, retrieving, and deleting comments.
Updating comments is not supported (nor is it available in the web
interface).

### Creating comments

To post a comment, create an `AtomEntry` object and insert it as follows:

```
AtomEntry comment;
comment = new AtomEntry();
comment.Title.Text = "This is my first comment";
comment.Content.Content = "This is my first comment";
Uri commentPostUri = new Uri("http://www.blogger.com/feeds/" + blogId + "/" + entryId + "/comments/default");
postedComment = service.Insert(commentPostUri, comment);
```

**Note**: Currently, you can only post comments to
a blog owned by the authenticated user.

**Note**: Setting a custom author for comments is
currently not supported. All new comments will appear as if they were created by
the currently authenticated user.

### Retrieving comments

You can retrieve the comments for a particular post from the post's comments feed URL:

```
static void ListEntryComments(Service service, Uri commentUri)
{
  if (commentUri != null)
  {
    // Retrieve all comments on a blog entry
    FeedQuery query = new FeedQuery();
    query.Uri = commentUri;
    AtomFeed feed = service.Query(query);
    foreach (AtomEntry entry in feed.Entries)
    {
      Console.WriteLine("  Comment Title: " + entry.Title.Text);
    }
  }
}
```

Or you can get the comments from all posts by using the blog's comments feed URL:

```
http://www.blogger.com/feeds/blogID/comments/default
```

### Deleting comments

To delete a comment, call the `Delete()` method on an existing
comment `AtomEntry` object like this:

```
static void DeleteComment(AtomEntry commentEntry)
{
  if (commentEntry != null)
  {
    // Delete the comment.
    commentEntry.Delete();
  }
}
```

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