public bool SaveTextF(string path)
{
    if (_isTextChanged)
    {
        if (string.IsNullOrWhiteSpace(path))
        {
            using (var dlg = new SaveFileDialog {Filter = "*.txt"})
            {
                if (dlg.ShowDialog() == DialogResult.OK)
                    path = dlg.FileName;
                else
                    return false;
            }
        }

        //call save methods on path
    }
    return true;
}

public bool SaveTextT(string path)
{
    if (!_isTextChanged) return true;
    if (string.IsNullOrWhiteSpace(path))
        using (var dlg = new SaveFileDialog {Filter = "*.txt"})
        {
            if (dlg.ShowDialog() != DialogResult.OK) return false;
            path = dlg.FileName;
        }
    //call save methods on path
    return true;
}

<Button  Click="btnClick_Event">Last</Button>

<Button Command="{Binding GoLast}">Last</Button>

using System;
using System.Windows.Input;

namespace MvvmHelpers
{
    // Ref.
    // - http://johnpapa.net/silverlight/5-simple-steps-to-commanding-in-silverlight/
    // - http://joshsmithonwpf.wordpress.com/2008/06/17/allowing-commandmanager-to-query-your-icommand-objects/
    public class DelegateCommand<T> : ICommand
    {
        readonly Func<T, bool> _canExecute;
        bool _canExecuteCache;
        readonly Action<T> _executeAction;

        public DelegateCommand(Action<T> executeAction, Func<T, bool> canExecute = null)
        {
            if (executeAction == null)
                throw new ArgumentNullException("executeAction");

            _executeAction = executeAction;
            _canExecute = canExecute;
        }

        public event EventHandler CanExecuteChanged
        {
            add { if (_canExecute != null) CommandManager.RequerySuggested += value; }
            remove { if (_canExecute != null) CommandManager.RequerySuggested -= value; }
        }

        public bool CanExecute(object parameter)
        {
            return _canExecute == null ? true : _canExecute((T)parameter);
        }

        public void Execute(object parameter)
        {
            _executeAction((T)parameter);
        }
    }
}

public DelegateCommand<string> GoLast { set; get; }

//in ctor
GoLast = new DelegateCommand<string>(goLast, canGoLast);

private bool canGoLast(string data)
{
    //ex.
    return ListViewGuiData.CurrentPage != ListViewGuiData.TotalPage - 1;
}

private void goLast(string data)
{
  //do something
}

using System.Collections.Generic;

using System.Linq;



namespace CircularDependencies

{

    public enum AggregateFunc

    {

        Sum,

        Avg

    }



    public class AggregateFuncCalculator

    {

        public decimal Calculate(IList<decimal> list, AggregateFunc func)

        {

            switch (func)

            {

                case AggregateFunc.Sum:

                    return getSum(list);

                case AggregateFunc.Avg:

                    return getAvg(list);

                default:

                    return 0m;

            }

        }



        private decimal getAvg(IList<decimal> list)

        {

            if (list == null || !list.Any()) return 0;

            return list.Sum() / list.Count;

        }



        private decimal getSum(IList<decimal> list)

        {

            if (list == null || !list.Any()) return 0;

            return list.Sum();

        }

    }

}

public interface IAggregateFunc

{

     decimal Calculate(IList<decimal> list);

}

public class Sum : IAggregateFunc

{

        public decimal Calculate(IList<decimal> list)

        {

            if (list == null || !list.Any()) return 0;

            return list.Sum();

        }

}



public class Avg : IAggregateFunc

{

        public decimal Calculate(IList<decimal> list)

        {

            if (list == null || !list.Any()) return 0;

            return list.Sum() / list.Count;

        }

}

public class AggregateFuncCalculator

{

        public decimal Calculate(IList<decimal> list, IAggregateFunc func)

        {

            return func.Calculate(list);

        }

}

public class NationalCodeClientValidator : ClientValidatorBase
    {
        #region Fields

        private NationalCodeValidator NationalCodeValidator => (NationalCodeValidator)Validator;

        #endregion Fields

        #region Methods

        #region Constructors

        public NationalCodeClientValidator(PropertyRule rule, IPropertyValidator validator) : base(rule, validator)
        {
        }

        #endregion Constructors

        #region Override

        public override void AddValidation(ClientModelValidationContext context)
        {
            MergeAttribute(context.Attributes, "data-val", "true");
            MergeAttribute(context.Attributes, "data-val-nationalcode", GetErrorMessage());
        }

        #endregion Override

        #region Utility

        private string GetErrorMessage()
        {
            var formatter = ValidatorOptions.MessageFormatterFactory().AppendPropertyName(Rule.GetDisplayName());
            string messageTemplate;
            try
            {
                messageTemplate = Validator.Options.ErrorMessageSource.GetString(null);
            }
            catch (FluentValidationMessageFormatException)
            {
                messageTemplate = ValidatorOptions.LanguageManager.GetStringForValidator<NotEmptyValidator>();
            }
            var message = formatter.BuildMessage(messageTemplate);
            return message;
        }

        #endregion Utility

        #endregion Methods
    }

public class NationalCodeValidator : PropertyValidator
    {
        #region Methods

        #region Constructors

        public NationalCodeValidator() : base(new LanguageStringSource(nameof(NationalCodeValidator)))
        {
        }

        #endregion Constructors

        #region Override

        protected override bool IsValid(PropertyValidatorContext context)
        {
            return true;
        }

        #endregion Override

        #endregion Methods
    }

.AddFluentValidation(option =>
            {
                option.RegisterValidatorsFromAssemblyContaining<CreateBankValidation>();
                option.ConfigureClientsideValidation(AddFluentValidationClientModelValidatorProvider());
            })

 private static Action<FluentValidationClientModelValidatorProvider> AddFluentValidationClientModelValidatorProvider()
        {
            return clientSideValidation =>
            {
                clientSideValidation.Add(typeof(NationalCodeValidator), (context, rule, validator) => new NationalCodeClientValidator(rule, validator));
            };
        }

// بررسی تایید کد ملی

function setCustomValidator() {
    $.validator.unobtrusive.adapters.add('nationalcode', [], function (options) {
        options.rules['nationalcode'] = {};
        options.messages['nationalcode'] = options.message;
    });
    $.validator.addMethod('nationalcode', function (value, element, parameters) {
        if (isValidIranianNationalCode(value)) return true;
        return false;
    });
}

      protected void btnGetData_Click(object sender, EventArgs e)
      {
          lblResult.Text = (Math.PI * double.Parse(txtRadius.Text) * double.Parse(txtRadius.Text)).ToString();
      }

using System;

namespace MVPTest
{
  public interface ICircleModel
  {
      double GetArea(double radius);
  }

  public class CModel : ICircleModel
  {     
      public double GetArea(double radius)
      {
          return Math.PI * radius * radius;
      }
  }
}

namespace MVPTest
{
  public interface IView
  {
      string RadiusText { get; set; }
      string ResultText { get; set; }
  }
}

namespace MVPTest
{
  public class CPresenter
  {
      IView _view;

      public CPresenter(IView view)
      {
          _view = view;
      }

      public void CalculateCircleArea()
      {
          CModel model = new CModel();
          _view.ResultText = model.GetArea(double.Parse(_view.RadiusText)).ToString();          
      }
  }
}

using System;

namespace MVPTest
{
  public partial class _Default : System.Web.UI.Page, IView
  {
      protected void Page_Load(object sender, EventArgs e)
      {
      }

      public string RadiusText
      {
          get { return txtRadius.Text; }
          set { txtRadius.Text = value; }
      }
      public string ResultText
      {
          get { return lblResult.Text; }
          set { lblResult.Text = value; }
      }

      protected void btnGetData_Click(object sender, EventArgs e)
      {
          CPresenter presenter = new CPresenter(this);
          presenter.CalculateCircleArea();
      }
  }
}

class Options {
  [Option('r', "read", Required = true,
    HelpText = "Input files to be processed.")]
  public IEnumerable<string> InputFiles { get; set; }

  // Omitting long name, default --verbose
  [Option(
    HelpText = "Prints all messages to standard output.")]
  public bool Verbose { get; set; }

  [Option(Default = "中文",
    HelpText = "Content language.")]
  public string Language { get; set; }

  [Value(0, MetaName = "offset",
    HelpText = "File offset.")]
  public long? Offset { get; set;}  
}