SYSLIB1017: A LogLevel value must be supplied in the LoggerMessage attribute or as a parameter to the logging method

The LoggerMessageAttribute attribute was applied to a method without a LogLevel value specified. When you do this, one argument to the logging method must be of that type so that the LogLevel value ends up being specified explicitly when calling the logging method.

Workarounds

Either specify a LogLevel value in the LoggerMessage attribute, or make one of the arguments of the logging method a LogLevel value.

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:

// 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:

<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>