How to read the Partitionkey of a container using Cosmosclient

One of the partameters of CreateItemStreamAsync is the partionkey value in current message. How do we access the current container’s partition key?

I see ContainerPropeties has the PartitionKeyPath property, but Container class doesn’t have a Resource properlty https://learn.microsoft.com/en-us/dotnet/api/microsoft.azure.cosmos.containerproperties?view=azure-dotnet

Container container = await client.GetDatabase("dbName").Containers.CreateAsync("MyCollection", "/country", 50000);
ContainerProperties containerProperties = container.Resource;

[NaluTripician]

Hello @praveenbarli hopefully the following will help you with your problem.

A when creating a Container for ComsosDB, you must specify at minimum two things. First is the id of the container. The second is the PartitionKeyPath. The PartitionKeyPathPath tells Cosmos where to look for the partition key value of every item you add into a Cosmos Container. This path can have any value also long as the items you add to Cosmos have that property.

For instance, let’s say you will be adding many of the following records to a Cosmos Database.

public record DatabaseItem(
            string id,
            string city, 
            string state,
            string zipcode
            );

When creating the Container that will be used to store these items you can that any of these values are the PartitionKeyPath. For example:

Container container = await db.CreateContainerAsync(
                id: "test",
                partitionKeyPath: "/city"
            );

or

Container container = await db.CreateContainerAsync(
                id: "test",
                partitionKeyPath: "/state"
            );

are both valid (but not the only) ways to create the Container.

Once a Container is created and we want to populate it with items we must make sure that the items have a property that matches the ParitionKeyPath we specified in the creation of the Container. Finding the ParitionKeyPath of a Container can be done like this: await container.ReadContainerAsync().PartitionKeyPath. When using the CreateItemStreamAsync method, we must specify two things. First is the stream containing the payload of the item we are creating, and second is the ParitionKey of that item.

Let’s look at the following example that details the creation of three items using the CreateItemStreamAsync method:

client = new CosmosClient(
                accountEndpoint: endpoint,
                authKeyOrResourceToken: key
            );

db = await client.CreateDatabaseIfNotExistsAsync(
                id: "testDB"
            );

container = await db.CreateContainerAsync(
                id: "test",
                partitionKeyPath: "/thisIsThePartitionKeyPath"
            );

using (ResponseMessage response = await container.CreateItemStreamAsync(
                               partitionKey: new PartitionKey("/TheParitionKey"),
                                              streamPayload: new MemoryStream(Encoding.UTF8.GetBytes("{\"id\":\"document1\",\"thisIsThePartitionKeyPath\":\"/TheParitionKey\"}"))
                                                         ))
{
            Console.WriteLine(response.StatusCode);
}

using (ResponseMessage response = await container.CreateItemStreamAsync(
                               partitionKey: new PartitionKey("/TheOtherParitionKey"),
                                              streamPayload: new MemoryStream(Encoding.UTF8.GetBytes("{\"id\":\"document2\",\"thisIsThePartitionKeyPath\":\"/TheOtherParitionKey\"}"))
                                                         ))
{
             Console.WriteLine(response.StatusCode);
}

using (ResponseMessage response = await container.CreateItemStreamAsync(
                               partitionKey: new PartitionKey("/TheOtherParitionKey"),
                                              streamPayload: new MemoryStream(Encoding.UTF8.GetBytes("{\"id\":\"document3\",\"thisIsThePartitionKeyPath\":\"/TheOtherParitionKey\"}"))
                                                         ))
{
             Console.WriteLine(response.StatusCode);
}

Here you can see the difference in what the PartitonKeyPath and PartitionKey is. In both cases the PartitionKeyPath stays the same, thisIsThePartitionKeyPath, while the values of the PartitionKey can change from item to item. However, as seen in the second and third items, they can have the same value. In summary, the PartitionKeyPath tells Cosmos where to find the value of the PartitionKey within an item and stays the same for each Container, while the PartitionKey is the actual value the items are partitioned on.

Please let me know if you have any further questions, if not feel free to close this issue.

[bartelink]

You should not call .Result - always use await to hop from a Task<X> to an X (you can search up an article on these sorts of things with .net Result await deadlock)