.NET Client - Qdrant

Installation

Install via NuGet:

dotnet add package Qdrant.Client

Or via Package Manager:

Install-Package Qdrant.Client

Quick Start

using Qdrant.Client;
using Qdrant.Client.Grpc;

// Connect to Qdrant
var client = new QdrantClient("localhost", 6334);

// Create collection
await client.CreateCollectionAsync(
    collectionName: "my_collection",
    vectorsConfig: new VectorParams
    {
        Size = 384,
        Distance = Distance.Cosine
    }
);

// Upsert points
await client.UpsertAsync(
    collectionName: "my_collection",
    points: new[]
    {
        new PointStruct
        {
            Id = 1,
            Vectors = new[] { 0.05f, 0.61f, 0.76f, 0.74f },
            Payload =
            {
                ["city"] = "Berlin",
                ["country"] = "Germany"
            }
        },
        new PointStruct
        {
            Id = 2,
            Vectors = new[] { 0.19f, 0.81f, 0.75f, 0.11f },
            Payload =
            {
                ["city"] = "London",
                ["country"] = "UK"
            }
        }
    }
);

// Search
var searchResults = await client.SearchAsync(
    collectionName: "my_collection",
    vector: new[] { 0.2f, 0.1f, 0.9f, 0.7f },
    limit: 3
);

foreach (var result in searchResults)
{
    Console.WriteLine($"ID: {result.Id}, Score: {result.Score}");
    Console.WriteLine($"Payload: {result.Payload}");
}

Repository

GitHub Repository

Official .NET client: qdrant/qdrant-dotnet

Client Initialization

Basic Connection

using Qdrant.Client;

// Connect via gRPC (recommended)
var client = new QdrantClient(host: "localhost", port: 6334);

// Connect to Qdrant Cloud
var cloudClient = new QdrantClient(
    host: "your-cluster.cloud.qdrant.io",
    port: 6334,
    https: true,
    apiKey: "your-api-key"
);

With Custom Options

using Grpc.Core;
using Qdrant.Client;

var channelOptions = new GrpcChannelOptions
{
    MaxReceiveMessageSize = 100 * 1024 * 1024, // 100MB
    MaxSendMessageSize = 100 * 1024 * 1024
};

var client = new QdrantClient(
    host: "localhost",
    port: 6334,
    grpcChannelOptions: channelOptions
);

Collection Management

Create Collection

using Qdrant.Client.Grpc;

await client.CreateCollectionAsync(
    collectionName: "my_collection",
    vectorsConfig: new VectorParams
    {
        Size = 768,
        Distance = Distance.Cosine,
        OnDisk = false,
        HnswConfig = new HnswConfigDiff
        {
            M = 16,
            EfConstruct = 100,
            FullScanThreshold = 10000
        }
    },
    replicationFactor: 2,
    writeConsistencyFactor: 1
);

Create with Multiple Vectors

await client.CreateCollectionAsync(
    collectionName: "multi_vector",
    vectorsConfig: new VectorParamsMap
    {
        Map =
        {
            ["text"] = new VectorParams
            {
                Size = 768,
                Distance = Distance.Cosine
            },
            ["image"] = new VectorParams
            {
                Size = 512,
                Distance = Distance.Euclid
            }
        }
    }
);

Get Collection Info

var info = await client.GetCollectionInfoAsync("my_collection");

Console.WriteLine($"Status: {info.Status}");
Console.WriteLine($"Vectors count: {info.VectorsCount}");
Console.WriteLine($"Points count: {info.PointsCount}");
Console.WriteLine($"Segments: {info.SegmentsCount}");

List Collections

var collections = await client.ListCollectionsAsync();

foreach (var collection in collections)
{
    Console.WriteLine(collection.Name);
}

Update Collection

await client.UpdateCollectionAsync(
    collectionName: "my_collection",
    optimizersConfig: new OptimizersConfigDiff
    {
        IndexingThreshold = 50000,
        MemmapThreshold = 100000
    }
);

Delete Collection

await client.DeleteCollectionAsync("my_collection");

Point Operations

Upsert Points

using Qdrant.Client.Grpc;

await client.UpsertAsync(
    collectionName: "my_collection",
    points: new[]
    {
        new PointStruct
        {
            Id = new PointId { Num = 1 },
            Vectors = new[] { 0.05f, 0.61f, 0.76f, 0.74f },
            Payload =
            {
                ["title"] = "Document 1",
                ["category"] = "technology",
                ["views"] = 1500,
                ["tags"] = new[] { "ai", "ml", "vector-db" }
            }
        },
        new PointStruct
        {
            Id = new PointId { Num = 2 },
            Vectors = new[] { 0.19f, 0.81f, 0.75f, 0.11f },
            Payload = { ["title"] = "Document 2" }
        }
    },
    wait: true
);

Upsert with GUID

var id = Guid.NewGuid();

await client.UpsertAsync(
    collectionName: "my_collection",
    points: new[]
    {
        new PointStruct
        {
            Id = new PointId { Uuid = id.ToString() },
            Vectors = new[] { 0.1f, 0.2f, 0.3f },
            Payload = { ["key"] = "value" }
        }
    }
);

Batch Upsert

const int batchSize = 100;
const int totalPoints = 10000;

for (int i = 0; i < totalPoints; i += batchSize)
{
    var points = Enumerable.Range(i, batchSize)
        .Select(j => new PointStruct
        {
            Id = new PointId { Num = (ulong)j },
            Vectors = Enumerable.Range(0, 384).Select(_ => (float)Random.Shared.NextDouble()).ToArray(),
            Payload = { ["index"] = j }
        })
        .ToArray();

    await client.UpsertAsync(
        collectionName: "my_collection",
        points: points,
        wait: false // Don't wait for faster throughput
    );
}

Get Points

var points = await client.RetrieveAsync(
    collectionName: "my_collection",
    ids: new[] { 1ul, 2ul, 3ul },
    withPayload: true,
    withVectors: true
);

foreach (var point in points)
{
    Console.WriteLine($"ID: {point.Id}");
    Console.WriteLine($"Vectors: {string.Join(", ", point.Vectors.Vector.Data)}");
    Console.WriteLine($"Payload: {point.Payload}");
}

Delete Points

using Qdrant.Client.Grpc;

// Delete by IDs
await client.DeleteAsync(
    collectionName: "my_collection",
    ids: new[] { 1ul, 2ul, 3ul }
);

// Delete by filter
await client.DeleteAsync(
    collectionName: "my_collection",
    filter: new Filter
    {
        Must =
        {
            new Condition
            {
                Field = new FieldCondition
                {
                    Key = "category",
                    Match = new Match { Keyword = "outdated" }
                }
            }
        }
    }
);

Search Operations

Basic Search

var results = await client.SearchAsync(
    collectionName: "my_collection",
    vector: new[] { 0.2f, 0.1f, 0.9f, 0.7f },
    limit: 10,
    payloadSelector: true,
    vectorsSelector: false
);

foreach (var result in results)
{
    Console.WriteLine($"ID: {result.Id}, Score: {result.Score}");
    Console.WriteLine($"Payload: {result.Payload}");
}

Search with Filtering

using Qdrant.Client.Grpc;

var results = await client.SearchAsync(
    collectionName: "my_collection",
    vector: new[] { 0.2f, 0.1f, 0.9f, 0.7f },
    filter: new Filter
    {
        Must =
        {
            new Condition
            {
                Field = new FieldCondition
                {
                    Key = "category",
                    Match = new Match { Keyword = "technology" }
                }
            },
            new Condition
            {
                Field = new FieldCondition
                {
                    Key = "views",
                    Range = new Range
                    {
                        Gte = 1000,
                        Lt = 10000
                    }
                }
            }
        }
    },
    limit: 5,
    scoreThreshold: 0.7f
);

Search with Parameters

var results = await client.SearchAsync(
    collectionName: "my_collection",
    vector: new[] { 0.2f, 0.1f, 0.9f, 0.7f },
    limit: 20,
    searchParams: new SearchParams
    {
        HnswEf = 128,
        Exact = false,
        Quantization = new QuantizationSearchParams
        {
            Ignore = false,
            Rescore = true,
            Oversampling = 2.0
        }
    }
);

Batch Search

var searchRequests = new[]
{
    new SearchPoints
    {
        CollectionName = "my_collection",
        Vector = { 0.2f, 0.1f, 0.9f },
        Limit = 5
    },
    new SearchPoints
    {
        CollectionName = "my_collection",
        Vector = { 0.5f, 0.3f, 0.2f },
        Limit = 10
    }
};

var batchResults = await client.SearchBatchAsync(
    collectionName: "my_collection",
    searches: searchRequests
);

for (int i = 0; i < batchResults.Length; i++)
{
    Console.WriteLine($"Results for query {i}:");
    foreach (var point in batchResults[i])
    {
        Console.WriteLine($"  ID: {point.Id}, Score: {point.Score}");
    }
}

Recommendations

var results = await client.RecommendAsync(
    collectionName: "my_collection",
    positiveIds: new[] { 1ul, 2ul, 3ul },
    negativeIds: new[] { 10ul },
    limit: 10,
    payloadSelector: true
);

foreach (var result in results)
{
    Console.WriteLine($"ID: {result.Id}, Score: {result.Score}");
}

Query API (Universal)

using Qdrant.Client.Grpc;

var results = await client.QueryAsync(
    collectionName: "my_collection",
    query: new float[] { 0.1f, 0.2f, 0.3f, 0.4f },
    limit: 10,
    withPayload: true
);

foreach (var result in results)
{
    Console.WriteLine($"ID: {result.Id}, Score: {result.Score}");
}

Payload Operations

Set Payload

await client.SetPayloadAsync(
    collectionName: "my_collection",
    payload: new Dictionary<string, Value>
    {
        ["new_field"] = "value",
        ["updated_at"] = "2024-01-01"
    },
    ids: new[] { 1ul, 2ul, 3ul }
);

Overwrite Payload

await client.OverwritePayloadAsync(
    collectionName: "my_collection",
    payload: new Dictionary<string, Value>
    {
        ["only_field"] = "value"
    },
    ids: new[] { 1ul, 2ul }
);

Delete Payload Keys

await client.DeletePayloadAsync(
    collectionName: "my_collection",
    keys: new[] { "old_field", "deprecated" },
    ids: new[] { 1ul, 2ul, 3ul }
);

Clear Payload

await client.ClearPayloadAsync(
    collectionName: "my_collection",
    ids: new[] { 1ul, 2ul, 3ul }
);

Scroll (Pagination)

PointId? offset = null;
var allPoints = new List<RetrievedPoint>();

while (true)
{
    var (points, nextOffset) = await client.ScrollAsync(
        collectionName: "my_collection",
        limit: 100,
        offset: offset,
        payloadSelector: true
    );

    allPoints.AddRange(points);
    offset = nextOffset;

    if (offset == null)
        break;
}

Console.WriteLine($"Total points: {allPoints.Count}");

Payload Indexing

using Qdrant.Client.Grpc;

// Create keyword index
await client.CreatePayloadIndexAsync(
    collectionName: "my_collection",
    fieldName: "category",
    schemaType: PayloadSchemaType.Keyword
);

// Create text index
await client.CreatePayloadIndexAsync(
    collectionName: "my_collection",
    fieldName: "description",
    schemaType: PayloadSchemaType.Text,
    indexParams: new PayloadIndexParams
    {
        TextIndexParams = new TextIndexParams
        {
            Tokenizer = TokenizerType.Word,
            Lowercase = true,
            MinTokenLen = 2,
            MaxTokenLen = 20
        }
    }
);

// Delete index
await client.DeletePayloadIndexAsync(
    collectionName: "my_collection",
    fieldName: "category"
);

Count Points

var count = await client.CountAsync(
    collectionName: "my_collection",
    exact: true
);

Console.WriteLine($"Total points: {count}");

// Count with filter
var filteredCount = await client.CountAsync(
    collectionName: "my_collection",
    filter: new Filter
    {
        Must =
        {
            new Condition
            {
                Field = new FieldCondition
                {
                    Key = "category",
                    Match = new Match { Keyword = "technology" }
                }
            }
        }
    },
    exact: true
);

Snapshots

// Create snapshot
var snapshot = await client.CreateSnapshotAsync("my_collection");
Console.WriteLine($"Snapshot name: {snapshot.Name}");

// List snapshots
var snapshots = await client.ListSnapshotsAsync("my_collection");
foreach (var snap in snapshots)
{
    Console.WriteLine($"Snapshot: {snap.Name}");
}

Error Handling

using Grpc.Core;
using Qdrant.Client;

try
{
    var info = await client.GetCollectionInfoAsync("nonexistent");
}
catch (RpcException ex) when (ex.StatusCode == StatusCode.NotFound)
{
    Console.WriteLine("Collection not found");
}
catch (RpcException ex)
{
    Console.WriteLine($"Error: {ex.StatusCode} - {ex.Status.Detail}");
}
catch (Exception ex)
{
    Console.WriteLine($"Unexpected error: {ex.Message}");
}

Strongly-Typed Payloads

using System.Text.Json;

public class DocumentPayload
{
    public string Title { get; set; }
    public string Category { get; set; }
    public int Views { get; set; }
    public List<string> Tags { get; set; }
}

// Serialize to payload
var document = new DocumentPayload
{
    Title = "Document 1",
    Category = "technology",
    Views = 1500,
    Tags = new List<string> { "ai", "ml" }
};

var payload = JsonSerializer.SerializeToDocument(document);

await client.UpsertAsync(
    collectionName: "my_collection",
    points: new[]
    {
        new PointStruct
        {
            Id = 1,
            Vectors = new[] { 0.1f, 0.2f, 0.3f },
            Payload = { /* Convert from JsonDocument */ }
        }
    }
);

// Deserialize from payload
var results = await client.SearchAsync(
    collectionName: "my_collection",
    vector: new[] { 0.2f, 0.1f, 0.9f },
    limit: 10
);

foreach (var result in results)
{
    var doc = JsonSerializer.Deserialize<DocumentPayload>(
        result.Payload.ToString()
    );
    Console.WriteLine($"Title: {doc.Title}, Views: {doc.Views}");
}

LINQ Integration

using System.Linq;

var results = await client.SearchAsync(
    collectionName: "my_collection",
    vector: new[] { 0.2f, 0.1f, 0.9f },
    limit: 100
);

// Use LINQ for post-processing
var topTech = results
    .Where(r => r.Payload.ContainsKey("category") && 
                r.Payload["category"].StringValue == "technology")
    .OrderByDescending(r => r.Score)
    .Take(10)
    .Select(r => new
    {
        Id = r.Id,
        Score = r.Score,
        Title = r.Payload["title"].StringValue
    });

foreach (var item in topTech)
{
    Console.WriteLine($"{item.Title}: {item.Score}");
}

Dependency Injection

using Microsoft.Extensions.DependencyInjection;
using Qdrant.Client;

public static class ServiceCollectionExtensions
{
    public static IServiceCollection AddQdrantClient(
        this IServiceCollection services,
        string host,
        int port)
    {
        services.AddSingleton<QdrantClient>(
            _ => new QdrantClient(host, port)
        );
        return services;
    }
}

// Usage in ASP.NET Core
public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddQdrantClient("localhost", 6334);
    }
}

// Inject in controller
public class SearchController : ControllerBase
{
    private readonly QdrantClient _client;

    public SearchController(QdrantClient client)
    {
        _client = client;
    }

    [HttpPost("search")]
    public async Task<IActionResult> Search([FromBody] float[] vector)
    {
        var results = await _client.SearchAsync(
            collectionName: "my_collection",
            vector: vector,
            limit: 10
        );
        return Ok(results);
    }
}

Async Enumerable

using System.Collections.Generic;
using System.Runtime.CompilerServices;

public async IAsyncEnumerable<RetrievedPoint> ScrollAllPointsAsync(
    QdrantClient client,
    string collectionName,
    [EnumeratorCancellation] CancellationToken cancellationToken = default)
{
    PointId? offset = null;

    while (!cancellationToken.IsCancellationRequested)
    {
        var (points, nextOffset) = await client.ScrollAsync(
            collectionName: collectionName,
            limit: 100,
            offset: offset
        );

        foreach (var point in points)
        {
            yield return point;
        }

        offset = nextOffset;
        if (offset == null)
            break;
    }
}

// Usage
await foreach (var point in ScrollAllPointsAsync(client, "my_collection"))
{
    Console.WriteLine($"ID: {point.Id}");
}

Best Practices

Performance tips:

Reuse QdrantClient instances (singleton pattern)
Use async/await throughout your application
Enable connection pooling with gRPC options
Use batch operations for bulk inserts
Set wait=false for faster upserts

Common issues:

Always handle RpcException for gRPC errors
Use CancellationToken for long-running operations
Dispose of resources properly (though client is reusable)
Ensure vector dimensions match collection config

Next Steps

Java Client

Java client documentation

gRPC API

Learn about gRPC protocol

Overview

REST API

gRPC API

Client Libraries

​Installation

​Quick Start

​Repository

GitHub Repository

​Client Initialization

​Basic Connection

​With Custom Options

​Collection Management

​Create Collection

​Create with Multiple Vectors

​Get Collection Info

​List Collections

​Update Collection

​Delete Collection

​Point Operations

​Upsert Points

​Upsert with GUID

​Batch Upsert

​Get Points

​Delete Points

​Search Operations

​Basic Search

​Search with Filtering

​Search with Parameters

​Batch Search

​Recommendations

​Query API (Universal)

​Payload Operations

​Set Payload

​Overwrite Payload

​Delete Payload Keys

​Clear Payload

​Scroll (Pagination)

​Payload Indexing

​Count Points

​Snapshots

​Error Handling

​Strongly-Typed Payloads

​LINQ Integration

​Dependency Injection

​Async Enumerable

​Best Practices

​Next Steps

Java Client

gRPC API

Installation

Quick Start

Repository

Client Initialization

Basic Connection

With Custom Options

Collection Management

Create Collection

Create with Multiple Vectors

Get Collection Info

List Collections

Update Collection

Delete Collection

Point Operations

Upsert Points

Upsert with GUID

Batch Upsert

Get Points

Delete Points

Search Operations

Basic Search

Search with Filtering

Search with Parameters

Batch Search

Recommendations

Query API (Universal)

Payload Operations

Set Payload

Overwrite Payload

Delete Payload Keys

Clear Payload

Scroll (Pagination)

Payload Indexing

Count Points

Snapshots

Error Handling

Strongly-Typed Payloads

LINQ Integration

Dependency Injection

Async Enumerable

Best Practices

Next Steps