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--- title: Azure DocumentDB Input Binding titleSuffix: Azure Functions description: Learn how to use Azure DocumentDB input binding in Azure Functions to retrieve and query documents from your database. Includes C# code examples and configuration guidance. author: sajeetharan ms.author: sasinnat ms.topic: reference ms.date: 11/19/2025 ms.custom: - sfi-ropc-nochange --- # Azure DocumentDB input binding for Azure Functions [!INCLUDE [functions-bindings-documentdb-preview](../../includes/functions-bindings-documentdb-preview.md)] The [Azure DocumentDB](/azure/documentdb/overview) input binding in Azure Functions lets you retrieve one or more documents from your database. This article explains how to configure and use the input binding with C# code examples, including querying collections and working with the MongoDB client. ## Prerequisites - An Azure subscription - If you don't have an Azure subscription, create a [free account](https://azure.microsoft.com/pricing/purchase-options/azure-account?cid=msft_learn) - An existing Azure DocumentDB cluster - If you don't have a cluster, create a [new cluster](/azure/documentdb/quickstart-portal) - [Change stream feature](/azure/documentdb/change-streams) enabled - Azure Functions .NET 8.0 project using the legacy in-process worker model - [`Microsoft.Azure.WebJobs.Extensions.AzureCosmosDb.Mongo` NuGet package](https://www.nuget.org/packages/Microsoft.Azure.WebJobs.Extensions.AzureCosmosDb.Mongo) - [`MongoDB.Driver` NuGet package](https://www.nuget.org/packages/MongoDB.Driver) ## Example This example shows an HTTP trigger function for an HTTP `GET` request. The function then uses an input binding to query the target Azure DocumentDB collection for documents that match the filter `{ "price": { "$gte": 150 }}`: ```csharp using System.Threading.Tasks; using Microsoft.AspNetCore.Mvc; using Microsoft.Azure.WebJobs; using Microsoft.Azure.WebJobs.Extensions.Http; using Microsoft.AspNetCore.Http; using Microsoft.Extensions.Logging; using Microsoft.Azure.WebJobs.Extensions.AzureCosmosDb.Mongo; using System.Collections.Generic; using MongoDB.Bson; public static class DocumentDBInput { [FunctionName(nameof(DocumentDBInput))] public static async Task<IActionResult> Run( [HttpTrigger(AuthorizationLevel.Function, "GET", Route = null)] HttpRequest request, [CosmosDBMongo(databaseName: "<database-name>", collectionName: "<collection-name>", ConnectionStringSetting = "<name-of-app-setting>", QueryString = "{{ \"price\": {{ \"$gte\": 150 }} }}")] IEnumerable<BsonDocument> documents, ILogger logger) { logger.LogInformation("C# Azure DocumentDB function queried a collection."); return new OkObjectResult(documents); } } ``` Alternatively, use a C# record or class type to represent documents returned from the collection: ```csharp using System.Threading.Tasks; using Microsoft.AspNetCore.Mvc; using Microsoft.Azure.WebJobs; using Microsoft.Azure.WebJobs.Extensions.Http; using Microsoft.AspNetCore.Http; using Microsoft.Extensions.Logging; using Microsoft.Azure.WebJobs.Extensions.AzureCosmosDb.Mongo; using System.Collections.Generic; using MongoDB.Bson; using MongoDB.Bson.Serialization.Attributes; public static class DocumentDBInput { [FunctionName(nameof(DocumentDBInput))] public static async Task<IActionResult> Run( [HttpTrigger(AuthorizationLevel.Function, "GET", Route = null)] HttpRequest request, [CosmosDBMongo(databaseName: "<database-name>", collectionName: "<collection-name>", ConnectionStringSetting = "<name-of-app-setting>", QueryString = "{{ \"price\": {{ \"$gte\": 150 }} }}")] IEnumerable<ProductDocument> products, ILogger logger) { logger.LogInformation("C# Azure DocumentDB function queried a collection."); return new OkObjectResult(products); } } public sealed record ProductDocument( [property: BsonId] [property: BsonRepresentation(BsonType.ObjectId)] string id, string name, string category, int quantity, decimal price, bool sale ); ``` ## Attributes This table describes the binding configuration properties of the `CosmosDBMongoTrigger` attribute. | Parameter | Description | | --- | --- | | **`FunctionId`** | (Optional) The ID of the trigger function. | | **`DatabaseName`** | (Optional) The name of the database targeted by the input. | | **`CollectionName`** | (Optional) The name of the collection in the database targeted by the input. | | **`ConnectionStringSetting`** | The name of an app setting or setting collection that specifies how to connect to the Azure DocumentDB cluster. | | **`QueryString`** | Defines the Mongo query expression used by the input binding return documents from the database. The query supports Azure Functions binding parameters. | > [!NOTE] > The `QueryString` parameter needs to be escaped with double curly brackets to account for Azure Function's built-in parameter binding. For more information, see [binding expressions and patterns](functions-bindings-expressions-patterns.md). ## Usage Use the `CosmosDBMongo` attribute to retrieve a set of documents from the collection: ```csharp [FunctionName(nameof(DocumentDBInput))] public static async Task<IActionResult> Run( [HttpTrigger(AuthorizationLevel.Function, "GET", Route = null)] HttpRequest request, [CosmosDBMongo(databaseName: "<database-name>", collectionName: "<collection-name>", ConnectionStringSetting = "<name-of-app-setting>")] IEnumerable<BsonDocument> documents, ILogger logger) { logger.LogInformation("C# Azure DocumentDB function queried a collection."); return new OkObjectResult(documents); } ``` Alternatively, work directly with the [MongoDB client](https://mongodb.github.io/mongo-csharp-driver/2.8/apidocs/html/T_MongoDB_Driver_IMongoClient.htm) in your function code: ```csharp [FunctionName(nameof(DocumentDBInput))] public static async Task<IActionResult> Run( [HttpTrigger(AuthorizationLevel.Function, "GET", Route = null)] HttpRequest request, [CosmosDBMongo(ConnectionStringSetting = "<name-of-app-setting>")] IMongoClient client, ILogger logger) { logger.LogInformation("C# Azure DocumentDB function got a client."); IMongoDatabase database = client.GetDatabase("<database-name>"); IMongoCollection<BsonDocument> collection = database.GetCollection<BsonDocument>("<collection-name>"); BsonDocument filter = []; // Empty filter to get all documents long count = await collection.CountDocumentsAsync(filter); return new OkObjectResult(new { documentsInCollection = count }); } ``` ## Related articles - [Azure DocumentDB](/azure/documentdb/overview) - [Azure DocumentDB bindings for Azure Functions](functions-bindings-documentdb.md) - [Azure DocumentDB trigger for Azure Functions](functions-bindings-documentdb-trigger.md) - [Azure DocumentDB output binding for Azure Functions](functions-bindings-documentdb-output.md)