Error report, please help me read what is the problem

Ahh, sorry about that. This should work on a table with FK references:

BEGIN TRANSACTION;
BEGIN TRY
    DECLARE @ErrorMessage NVARCHAR(MAX);
    DECLARE @ErrorSeverity INT;
    DECLARE @ErrorState INT;

    DELETE FROM dbo.Tasks;

    COMMIT TRANSACTION;
END TRY
BEGIN CATCH
    IF @@TRANCOUNT > 0
    BEGIN
        ROLLBACK TRANSACTION;

        SET @ErrorMessage = ERROR_MESSAGE();
        SET @ErrorSeverity = ERROR_SEVERITY();
        SET @ErrorState = ERROR_STATE();
        RAISERROR(@ErrorMessage, @ErrorSeverity, @ErrorState);
    END;
END CATCH;