<PackageReference Include="System.Configuration.ConfigurationManager" Version="10.0.2" />

System.Configuration.CallbackValidatorAttribute

Specifies a CallbackValidator object to use for code validation. This class cannot be inherited.
public string CallbackMethodName { get; set; }

Gets or sets the name of the callback method.

public Type Type { get; set; }

Gets or sets the type of the validator.

Initializes a new instance of the CallbackValidatorAttribute class.