public async Task InsertWithDuplicateKey()
{
/* In a concurrent system, your app might try to save a document that
* has a duplicate value on a field that is marked unique. When this
* happens, MongoDB returns a Duplicate Key error.
*
* To show this, let's add a Theater document to a collection, and
* then add a new document with the same Id value as the first
* Theater. We're using the Id field because it maps to the _id field
* in Mongo, and _id is a field that is always marked as unique.
*/
var testTheater = new Theater(10101010, "234 Bar Ave.", "Wishywashy", "WY", "87654");
await _theatersCollection.InsertOneAsync(testTheater);
/* You may recall from a previous lesson that in our Theater class,
* we don't assign a value to the Id field; we let MongoDB do that
* for us. When the call to InsertOne or InsertOneAsync returns,
* our new Theater object has that field populated for us!
*
* So let's now use that existing Id value to create and insert a
* new Theater object:
*/
var myNewTheater = new Theater()
{
Id = testTheater.Id
};
/* This call should fail with an exception:
*/
Assert.Throws <MongoWriteException>(() =>
_theatersCollection.InsertOne(myNewTheater));
/* Now that we've confirmed this, we can wrap our writes in
* try-catch blocks to handle exceptions accordingly. While a Duplicate
* Key error is unlikely to happen, especially if you let MongoDB
* handle assigning a value to the _id field for you, it's always a
* best practice to use try-catch blocks. And if you are managing
* a field of unique values in your code, you'll definitely want
* to be handling this exception!
*/
try
{
await _theatersCollection.InsertOneAsync(myNewTheater);
}
catch (MongoWriteException ex)
{
/* There are, of course, other potential write errors, so
* let's make sure we really caught a dupliate key error:
*/
Assert.IsTrue(ex.Message.Contains("E11000 duplicate key error"));
/* If you have a custom process for generating unique key values,
* this would be a good place to change the Id value and re-try
* the Insert.
*/
}
}
public async Task CreateMovieAsync()
{
/* There are two methods for writing documents with the MongoDB
* driver: InsertOne and InsertMany, as well as the Async versions
* of those two methods. In this lesson, I'll show you how to use
* the Async methods in a couple of different ways.
*
* Let's start with a simple example. We want to add a new movie
* theater to the "theaters" collection. Let's first take a look at
* the Theater mapping class. It has Id, TheaterId, and Location
* properties. The Location property is an object that contains an
* Address object and Geo information, which we won't worry about
* in this lesson.
*
* With that bit of information, let's create a new instance of the
* Theater class, using the constructor that takes in a TheaterId and
* various Address components:
*
*/
var newTheater = new Theater(27777,
"4 Privet Drive",
"Little Whinging",
"LA",
"343434");
// And now we call InsertOneAsync() to add it to the collection:
await _theatersCollection.InsertOneAsync(newTheater);
/* Here's something you should be aware of. In the constructor for
* the Theater object, we don't set the Id property. Instead,
* we let MongoDB create one and assign it for us as part of the
* Insert call. We can check that property as soon as the InsertOne
* returns:
*/
Assert.IsNotEmpty(newTheater.Id.ToString());
/* Adding multiple theaters to the collection is just as easy.
* Let's add a group of 3 new theaters that have just been built.
* First, we create the Theater objects:
*/
var theater1 = new Theater(27017, "1 Foo Street", "Dingledongle", "DE", "45678");
var theater2 = new Theater(27018, "234 Bar Ave.", "Wishywashy", "WY", "87654");
var theater3 = new Theater(27019, "75 Birthday Road", "Viejo Amigo", "CA", "99887");
/* And then we call InsertManyAsync, passing in a new List of
* those Theater objects:
*/
await _theatersCollection.InsertManyAsync(
new List <Theater>()
{
theater1, theater2, theater3
}
);
/* Let's make sure everything worked. */
var newTheaters = await _theatersCollection.Find <Theater>(
Builders <Theater> .Filter.Gte(t => t.TheaterId, 27017)
& Builders <Theater> .Filter.Lte(t => t.TheaterId, 27019))
.ToListAsync();
Assert.AreEqual(3, newTheaters.Count);
Assert.AreEqual("1 Foo Street",
newTheaters.First().Location.Address.Street1);
Assert.AreEqual("Viejo Amigo",
newTheaters.Last().Location.Address.City);
/* So that's all there is to writing new documents to a MongoDB
* collection. In the next lesson, we'll look at updating
* existing documents.
*/
}
