Accessing Google Spreadsheets with C# using Google Data API

According to the .NET user guide:

Download the .NET client library:

Add these using statements:

using Google.GData.Client;
using Google.GData.Extensions;
using Google.GData.Spreadsheets;

Authenticate:

SpreadsheetsService myService = new SpreadsheetsService("exampleCo-exampleApp-1");
myService.setUserCredentials("[email protected]", "mypassword");

Get a list of spreadsheets:

SpreadsheetQuery query = new SpreadsheetQuery();
SpreadsheetFeed feed = myService.Query(query);

Console.WriteLine("Your spreadsheets: ");
foreach (SpreadsheetEntry entry in feed.Entries)
{
    Console.WriteLine(entry.Title.Text);
}

Given a SpreadsheetEntry you've already retrieved, you can get a list of all worksheets in this spreadsheet as follows:

AtomLink link = entry.Links.FindService(GDataSpreadsheetsNameTable.WorksheetRel, null);

WorksheetQuery query = new WorksheetQuery(link.HRef.ToString());
WorksheetFeed feed = service.Query(query);

foreach (WorksheetEntry worksheet in feed.Entries)
{
    Console.WriteLine(worksheet.Title.Text);
}

And get a cell based feed:

AtomLink cellFeedLink = worksheetentry.Links.FindService(GDataSpreadsheetsNameTable.CellRel, null);

CellQuery query = new CellQuery(cellFeedLink.HRef.ToString());
CellFeed feed = service.Query(query);

Console.WriteLine("Cells in this worksheet:");
foreach (CellEntry curCell in feed.Entries)
{
    Console.WriteLine("Row {0}, column {1}: {2}", curCell.Cell.Row,
        curCell.Cell.Column, curCell.Cell.Value);
}

I wrote a simple wrapper around Google's .Net client library, it exposes a simpler database-like interface, with strongly-typed record types. Here's some sample code:

public class Entity {
    public int IntProp { get; set; }
    public string StringProp { get; set; }
}

var e1 = new Entity { IntProp = 2 };
var e2 = new Entity { StringProp = "hello" };
var client = new DatabaseClient("[email protected]", "password");
const string dbName = "IntegrationTests";
Console.WriteLine("Opening or creating database");
db = client.GetDatabase(dbName) ?? client.CreateDatabase(dbName); // databases are spreadsheets
const string tableName = "IntegrationTests";
Console.WriteLine("Opening or creating table");
table = db.GetTable<Entity>(tableName) ?? db.CreateTable<Entity>(tableName); // tables are worksheets
table.DeleteAll();
table.Add(e1);
table.Add(e2);
var r1 = table.Get(1);

There's also a LINQ provider that translates to google's structured query operators:

var q = from r in table.AsQueryable()
        where r.IntProp > -1000 && r.StringProp == "hello"
        orderby r.IntProp
        select r;

(Jun-Nov 2016) The question and its answers are now out-of-date as: 1) GData APIs are the previous generation of Google APIs. While not all GData APIs have been deprecated, all the latest Google APIs do not use the Google Data Protocol; and 2) there is a new Google Sheets API v4 (also not GData).

Moving forward from here, you need to get the Google APIs Client Library for .NET and use the latest Sheets API, which is much more powerful and flexible than any previous API. Here's a C# code sample to help get you started. Also check the .NET reference docs for the Sheets API and the .NET Google APIs Client Library developers guide.

If you're not allergic to Python (if you are, just pretend it's pseudocode ;) ), I made several videos with slightly longer, more "real-world" examples of using the API you can learn from and migrate to C# if desired:

• Migrating SQL data to a Sheet (code deep dive post)
• Formatting text using the Sheets API (code deep dive post)
• Generating slides from spreadsheet data (code deep dive post)
• Those and others in the Sheets API video library

This Twilio blog page made on March 24, 2017 by Marcos Placona may be helpful.

Google Spreadsheets and .NET Core

It references Google.Api.Sheets.v4 and OAuth2.

You can do what you're asking several ways:

1. Using Google's spreadsheet C# library (as in Tacoman667's answer) to fetch a ListFeed which can return a list of rows (ListEntry in Google parlance) each of which has a list of name-value pairs. The Google spreadsheet API (http://code.google.com/apis/spreadsheets/code.html) documentation has more than enough information to get you started.

2. Using the Google visualization API which lets you submit more sophisticated (almost like SQL) queries to fetch only the rows/columns you require.

3. The spreadsheet contents are returned as Atom feeds so you can use XPath or SAX parsing to extract the contents of a list feed. There is an example of doing it this way (in Java and Javascript only though I'm afraid) at http://gqlx.twyst.co.za.