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Fix: Cryptic "No constructor" Error When ILoggerFactory Is Not Registered (Issue #1153) #1157

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Merged
jbogard merged 5 commits into from
Feb 22, 2026
+26 −9
Merged

Fix: Cryptic "No constructor" Error When ILoggerFactory Is Not Registered (Issue #1153) #1157

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e1f6caa
Applying fix
jbogard Feb 22, 2026
0b4fa68
Initial plan
Copilot Feb 22, 2026
e0ae1ac
Simplify CheckLicense to use GetRequiredService instead of fallback l…
Copilot Feb 22, 2026
25ffe81
Merge pull request #1158 from LuckyPennySoftware/copilot/sub-pr-1157
jbogard Feb 22, 2026
883d940
Explicitly registering with types
jbogard Feb 22, 2026
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2 changes: 1 addition & 1 deletion src/MediatR/MicrosoftExtensionsDI/MediatRServiceCollectionExtensions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -66,7 +66,7 @@ internal static void CheckLicense(this IServiceProvider serviceProvider)
serviceProvider.GetRequiredService<MediatRServiceConfiguration>(),
serviceProvider.GetRequiredService<ILoggerFactory>()
);
var licenseValidator = serviceProvider.GetService<LicenseValidator>()
var licenseValidator = serviceProvider.GetService<LicenseValidator>()
?? new LicenseValidator(serviceProvider.GetRequiredService<ILoggerFactory>());
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Copilot AI Feb 22, 2026

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The PR description states that this method should be simplified to use GetRequiredService for both licenseAccessor and licenseValidator, removing the fallback logic with ?? new LicenseAccessor(...) and ?? new LicenseValidator(...). However, this change was not implemented - only a trailing whitespace was removed from line 69. The fallback logic on lines 65-70 should be replaced with: var licenseAccessor = serviceProvider.GetRequiredService<LicenseAccessor>(); and var licenseValidator = serviceProvider.GetRequiredService<LicenseValidator>(); as described in the PR description.

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@jbogard jbogard Feb 22, 2026

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@copilot open a new pull request to apply changes based on this feedback


var license = licenseAccessor.Current;
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22 changes: 20 additions & 2 deletions src/MediatR/Registration/ServiceRegistrar.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
using MediatR.Pipeline;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection.Extensions;
using Microsoft.Extensions.Logging;

namespace MediatR.Registration;

Expand Down Expand Up @@ -470,8 +471,25 @@ public static void AddRequiredServices(IServiceCollection services, MediatRServi
MediatRServiceCollectionExtensions.LicenseChecked = false;

services.TryAddSingleton(serviceConfiguration);
services.TryAddSingleton<LicenseAccessor>();
services.TryAddSingleton<LicenseValidator>();
services.TryAddSingleton(static sp =>
{
var loggerFactory = sp.GetService<ILoggerFactory>()
?? throw new InvalidOperationException(
"MediatR requires ILoggerFactory to be registered. " +
"Call services.AddLogging() before services.AddMediatR().");
Comment on lines +476 to +479
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Copilot AI Feb 22, 2026

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New behavior is being introduced here (custom InvalidOperationException when ILoggerFactory is missing). There isn’t currently a test asserting this specific failure mode/message (the suite generally calls AddFakeLogging). Adding a focused test that omits logging and asserts the thrown message would help prevent regressions back to the cryptic "No constructor" error.

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Comment on lines +476 to +479
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Copilot AI Feb 22, 2026

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The exception message says to call services.AddLogging() before services.AddMediatR(), but registration order doesn’t actually matter as long as ILoggerFactory is registered before the provider is built/resolution happens (e.g., tests call AddRequiredServices before AddFakeLogging). Consider rewording to avoid implying a required ordering (e.g., “Ensure ILoggerFactory is registered (services.AddLogging())”).

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var config = sp.GetService<MediatRServiceConfiguration>();
return config != null
? new LicenseAccessor(config, loggerFactory)
: new LicenseAccessor(loggerFactory);
Comment on lines +480 to +483
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Copilot AI Feb 22, 2026

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MediatRServiceConfiguration is always registered just above via services.TryAddSingleton(serviceConfiguration), so sp.GetService<MediatRServiceConfiguration>() should never be null here. This makes the conditional and the new LicenseAccessor(loggerFactory) branch effectively dead code; consider switching to GetRequiredService<MediatRServiceConfiguration>() and always using the (config, loggerFactory) constructor to simplify.

Suggested change
var config = sp.GetService<MediatRServiceConfiguration>();
return config != null
? new LicenseAccessor(config, loggerFactory)
: new LicenseAccessor(loggerFactory);
var config = sp.GetRequiredService<MediatRServiceConfiguration>();
return new LicenseAccessor(config, loggerFactory);

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});
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Copilot AI Feb 22, 2026

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The TryAddSingleton call is missing the type parameter. This will not register LicenseAccessor in the DI container correctly. Change line 474 to: services.TryAddSingleton<LicenseAccessor>(static sp =>

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services.TryAddSingleton(static sp =>
{
var loggerFactory = sp.GetService<ILoggerFactory>()
?? throw new InvalidOperationException(
"MediatR requires ILoggerFactory to be registered. " +
"Call services.AddLogging() before services.AddMediatR().");
return new LicenseValidator(loggerFactory);
});
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Copilot AI Feb 22, 2026

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The TryAddSingleton call is missing the type parameter. This will not register LicenseValidator in the DI container correctly. Change line 485 to: services.TryAddSingleton<LicenseValidator>(static sp =>

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var notificationPublisherServiceDescriptor = serviceConfiguration.NotificationPublisherType != null
? new ServiceDescriptor(typeof(INotificationPublisher), serviceConfiguration.NotificationPublisherType, serviceConfiguration.Lifetime)
Expand Down