How can I reference the Configuration from CustomDomainCommand Header button?

This isn't related to the VAF at all, but how fields instantiated like that can access instance members.  Instead: move the code to the constructor:

public class VaultApplication
        : MFiles.VAF.Extensions.ConfigurableVaultApplicationBase<Configuration>

    {


        public CustomDomainCommand cmdHeaderButtonCommand { get; }
        
        public VaultApplication()
        {
            this.cmdHeaderButtonCommand = new CustomDomainCommand
            {
                ID = "cmdHeaderButtonCommand",
                Execute = (c, o) =>
                {
                    string returntest = this.Configuration.MyStringValue;
                    o.ShowMessage(""+returntest);
                },
                DisplayName = "Test Contents",
                Locations = new List<ICommandLocation>
                {
                    new ButtonBarCommandLocation()
                }
            }
        };

        /// <inheritdoc />
        public override IEnumerable<CustomDomainCommand> GetCommands(IConfigurationRequestContext context)
        {
            return new List<CustomDomainCommand>(base.GetCommands(context))
            {
            this.cmdHeaderButtonCommand,
            };
        }

    }

An alternative approach is to use the new functionality recently added to the Extensions, which cuts out a lot of that boilerplate:

public class VaultApplication 
: MFiles.VAF.Extensions.ConfigurableVaultApplicationBase<Configuration>
{

	[CustomCommand("Test Contents")]
	[ButtonBarCommandLocation]
	public void SayHello
	(
		IConfigurationRequestContext context, 
		ClientOperations operations
	)
	{
        string returntest = this.Configuration.MyStringValue;
        operations.ShowMessage(""+returntest);
	}
}

Thank you! and the new functionality is beautifully simple.

It doesn't do anything more clever than plumb together everything via those attributes.  The VAF does all the hard work.

Glad it's working though.

I had a secondary issue which drove the original question where I had a second class in the main namespace.  was trying to pull in from the configuration class.  I solved that issue by passing "this.Configuration" through to that class as "Configurat Config" and then i could just Config.<> without problems!