C# Signature:

[DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
static extern bool CopyFile(string lpExistingFileName, string lpNewFileName, bool bFailIfExists);

[DllImport("kernel32.dll", CharSet = CharSet.Unicode, CallingConvention = CallingConvention.StdCall, SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool CopyFile(
  [MarshalAs(UnmanagedType.LPWStr)]string lpExistingFileName,
  [MarshalAs(UnmanagedType.LPWStr)]string lpNewFileName,
  [MarshalAs(UnmanagedType.Bool)]bool bFailIfExists);

VB.NET Signature:

<DllImport("kernel32.dll", CharSet := CharSet.Unicode, CallingConvention := CallingConvention.StdCall, SetLastError := True)>
Shared Function CopyFile(<MarshalAs(UnmanagedType.LPWStr)> ByVal lpExistingFileName As String, <MarshalAs(UnmanagedType.LPWStr)> ByVal lpNewFileName As String, <MarshalAs(UnmanagedType.Bool)> ByVal bFailIfExists As Boolean) As <MarshalAs(UnmanagedType.Bool)> Boolean
End Function

User-Defined Types:

None.

Notes:

None.

Tips & Tricks:

Please add some!

Sample Code - C# - sivakumar.keerthi

using System;

using System.Drawing;

using System.Collections;

using System.ComponentModel;

using System.Windows.Forms;

using System.Data;

using System.Runtime.InteropServices;

using System.Diagnostics;

namespace WindowsApplication1

{

    /// <summary>
    /// Summary description for Form1.
    /// </summary>
    public class Form1 : System.Windows.Forms.Form
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        [DllImport("kernel32.dll")]
        static extern bool CopyFile(string lpExistingFileName, string lpNewFileName,bool bFailIfExists);

        private System.ComponentModel.Container components = null;

        public Form1()
        {
            //
            // Required for Windows Form Designer support
            //
            InitializeComponent();
            //
            // TODO: Add any constructor code after InitializeComponent call
            //
        }

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        protected override void Dispose( bool disposing )
        {
            if( disposing )
            {
                if (components != null)
                {
                    components.Dispose();
                }
            }
            base.Dispose( disposing );
        }

        #region Windows Form Designer generated code
        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.SuspendLayout();
            //
            // Form1
            //
            this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
            this.ClientSize = new System.Drawing.Size(528, 266);
            this.Name = "Form1";
            this.Text = "Form1";
            this.Load += new System.EventHandler(this.Form1_Load);
            this.ResumeLayout(false);

        }
        #endregion

        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.Run(new Form1());
        }

        private void Form1_Load(object sender, System.EventArgs e)
        {
            //bFailIfExists
            //true or false - if destination file not exists, it will create and write the contents of file1 to it.
            //true - If destination file exists it won't write the contents of file1 to file2.
            //false - If destination file exists it will write the contents of file1 to file2.

            CopyFile( @"C:\Source.txt" , @"C:\Destination.txt" , true );
        }
    }

}

Alternative Managed API:

public static void System.IO.File.Copy(System.String sourceFileName , System.String destFileName , System.Boolean overwrite)