動作環境

Windows 8.1 Pro (64bit)
Microsoft Visual Studio 2017 Community
Sublime Text 2

ファイルのコピー方法に関して。

参考

二つ目のFile.Copy()はoverwriteを指定できる。

code

MainWindow.xaml

<Window x:Class="_171115_t0940_filecopy.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:_171115_t0940_filecopy"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Button Name="B_filecopy" Height="30" Content="file copy" Click="B_filecopy_Click"/>
    </Grid>
</Window>

MainWindow.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
// 以下を追加
using System.IO;

namespace _171115_t0940_filecopy
{
    /// <summary>
    /// MainWindow.xaml の相互作用ロジック
    /// </summary>
    public partial class MainWindow : Window
    {
        private readonly string kFromFile = "D:\\FileProcess_171115\\171010.csv";
        private readonly string kToFile = "D:\\FileProcess_171115\\171015.csv";

        public MainWindow()
        {
            InitializeComponent();
        }

        private void copyFile_noOverwrite()
        {
            try
            {
                File.Copy(kFromFile, kToFile);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString()); // (1)
            }
        }

        private void copyFile_overwrite()
        {
            try
            {
                File.Copy(kFromFile, kToFile, overwrite: true);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString()); // (2)
            }
        }

        private void B_filecopy_Click(object sender, RoutedEventArgs e)
        {
            copyFile_overwrite();
            copyFile_noOverwrite();
        }
    }
}

File.Copy(String, String)実行時にファイルが既存するためにエラーが出る。