SYSLIB1019: Couldn't find a field of type ILogger

When a logging method definition doesn't explicitly include a parameter of type ILogger, then the type containing the logging method must have one and only one field of type ILogger. The ILogger will be used as the target for log messages.

Workarounds

Ensure the type containing the logging method includes a field of type ILogger or include a parameter of type ILogger in the logging method signature.

Note

If you get this error but your class uses a primary constructor that takes an ILogger, you can resolve the error by adding an ILogger field as follows:

C#

public partial class Foo(ILogger<Foo> logger) {
    // Workaround for https://github.com/dotnet/runtime/issues/91121.
    private readonly ILogger _logger = logger;
}

Suppress warnings

It's recommended that you use one of the workarounds when possible. However, if you cannot change your code, you can suppress the warning through a #pragma directive or a <NoWarn> project setting. If the SYSLIB1XXX source generator diagnostic doesn't surface as an error, you can suppress the warning in code or in your project file.

To suppress the warnings in code:

C#

// Disable the warning.
#pragma warning disable SYSLIB1006

// Code that generates compiler diagnostic.
// ...

// Re-enable the warning.
#pragma warning restore SYSLIB1006

To suppress the warnings in a project file:

XML

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
   <TargetFramework>net6.0</TargetFramework>
   <!-- NoWarn below suppresses SYSLIB1002 project-wide -->
   <NoWarn>$(NoWarn);SYSLIB1002</NoWarn>
   <!-- To suppress multiple warnings, you can use multiple NoWarn elements -->
   <NoWarn>$(NoWarn);SYSLIB1002</NoWarn>
   <NoWarn>$(NoWarn);SYSLIB1006</NoWarn>
   <!-- Alternatively, you can suppress multiple warnings by using a semicolon-delimited list -->
   <NoWarn>$(NoWarn);SYSLIB1002;SYSLIB1006;SYSLIB1007</NoWarn>
  </PropertyGroup>
</Project>