dotnetcore/CAP · error · InvalidOperationException

Unable to extract namespace from connection string.

Error message

Unable to extract namespace from connection string.

What it means

When only a connection string is provided (no namespace), GetBrokerAddress tries to extract the host from the Endpoint=sb://... part of the connection string. If extraction fails — the connection string is malformed or lacks an Endpoint component — it throws InvalidOperationException.

Solutions

1. Use a full namespace connection string that starts with Endpoint=sb://<namespace>.servicebus.windows.net/;SharedAccessKeyName=...;SharedAccessKey=...
2. Alternatively set opt.Namespace directly so the connection string does not need parsing
3. Validate the connection string format (starts with 'Endpoint=sb://') before configuring CAP
4. Re-copy the connection string from Azure Portal -> Service Bus Namespace -> Shared access policies (root policy for namespace-level access)

Example fix

// before
options.UseAzureServiceBus("SharedAccessKeyName=RootManageSharedAccessKey;SharedAccessKey=abc123"); // no Endpoint
// after
options.UseAzureServiceBus("Endpoint=sb://myns.servicebus.windows.net/;SharedAccessKeyName=RootManageSharedAccessKey;SharedAccessKey=abc123");
// or simply
options.UseAzureServiceBus(opt => opt.Namespace = "myns.servicebus.windows.net");

if (string.IsNullOrWhiteSpace(ns) && !(cs?.StartsWith("Endpoint=sb://", StringComparison.OrdinalIgnoreCase) ?? false)) throw new InvalidOperationException("Connection string must contain Endpoint=sb:// when namespace is not set");

bool IsNamespaceConnectionString(string? cs) => cs?.StartsWith("Endpoint=sb://", StringComparison.OrdinalIgnoreCase) == true;

try { var addr = ServiceBusHelpers.GetBrokerAddress(cs, null); } catch (InvalidOperationException ex) when (ex.Message.Contains("Unable to extract namespace")) { logger.LogCritical(ex, "Connection string lacks Endpoint=sb://"); throw; }

When it happens

Trigger: Passing a connection string without Endpoint=sb://<host>/ (e.g. only SharedAccessKeyName/SharedAccessKey pairs, a truncated string, or an Event-Hub-style string with a different endpoint key) while Namespace is null/empty.

Common situations: Copying an SAS entity connection string that still includes EntityPath but was truncated; pasting keys from the portal without the Endpoint segment; whitespace/encoding corruption when injecting the string via environment variables; mistakenly using a storage or Event Hubs connection string.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• Value cannot be null. (Parameter 'options')
• Value cannot be null. (Parameter 'topics')
• Value cannot be null. (Parameter 'connectionString')
• Value cannot be null. (Parameter 'configure')
• Either connection string or namespace are required.

AI-assisted analysis of dotnetcore/CAP@e52b8508e5 (2026-09-14). Data as JSON: /api/errors/58f76632a3057c84. Report an issue: GitHub.

Appendix: source

Thrown at src/DotNetCore.CAP.AzureServiceBus/Helpers/ServiceBusHelpers.cs:20

using DotNetCore.CAP.Transport;

namespace DotNetCore.CAP.AzureServiceBus.Helpers;

public static class ServiceBusHelpers
{
    public static BrokerAddress GetBrokerAddress(string? connectionString, string? @namespace)
    {
        var host = (@namespace, connectionString) switch
        {
            _ when string.IsNullOrWhiteSpace(@namespace) && string.IsNullOrWhiteSpace(connectionString)
                => throw new ArgumentException("Either connection string or namespace are required."),
            _ when string.IsNullOrWhiteSpace(connectionString)
                   || (!string.IsNullOrWhiteSpace(@namespace) && !string.IsNullOrWhiteSpace(connectionString))
                => @namespace!,
            _ when string.IsNullOrWhiteSpace(@namespace)
                => TryGetEndpointFromConnectionString(connectionString, out var extractedValue)
                    ? extractedValue!
                    : throw new InvalidOperationException("Unable to extract namespace from connection string."),
            _ => throw new InvalidOperationException("Unhandled case in switch expression.")
        };

        return new BrokerAddress("servicebus", host);
    }


    private static bool TryGetEndpointFromConnectionString(string? connectionString, out string? @namespace)
    {
        @namespace = string.Empty;

        if (string.IsNullOrWhiteSpace(connectionString))
            return false;

        var keyValuePairs = connectionString.Split(';');

        foreach (var kvp in keyValuePairs)
        {

View on GitHub (pinned to e52b8508e5)