C# | CopyTo() Method

In C#, CopyTo() method is a string method. It is used to copy a specified number of characters from a specified position in the string and it copies the characters of this string into a array of Unicode characters.

Syntax:

public void CopyTo(int sourceIndex, char[] destination, 
                      int destinationIndex, int count)

Explanation: CopyTo() method will copied the count characters from the sourceIndex position to the destinationIndex position of destination character array. This method accepts four parameters as follows :

1. sourceIndex : Index of String to be copied. And its type is System.Int32 .
2. destination : It is the array of Unicode characters to which characters will be copied. Its type is System.Char[].
3. destinationIndex : It is starting index of array from where the copy operation begins. Its type is System.Int32.
4. count : It is the number of characters which will copy to destination. Its type is System.Int32.

Examples :

Input : str  = "GeeksForGeeks"
        char [] Copystring = new char[15];     
        str.CopyTo(5, Copystring, 0, 3);
Output: For

Input : str2 = "GeeksForGeeks";
        char [] Copystring = {'H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd'};
        str2.CopyTo(8, Copystring, 6, 5);
Output: Hello Geeks

Below example programs illustrate the ToCopy() Method :

• Example 1:

  // C# program to illustrate the
  // ToCopy() string method
  using System;
  
  class Geeks {
  
      // Main Method
      public static void Main()
      {
          string str = "GeeksForGeeks";
          char[] dest = new char[15];
  
          // str index 5 to 5+3 has to
          // copy into Copystring
          // 3 is no. of character
          // 0 is start index of Copystring
          str.CopyTo(5, dest, 0, 3);
  
          // Displaying String
          Console.Write("The Copied String in dest Variable is: ");
          Console.WriteLine(dest);
      }
  }
  Output:

  The Copied String in dest Variable is: For
  

• Example 2:

  // C# program to illustrate the
  // ToCopy() string method
  using System;
  
  class Geeks {
  
      // Main Method
      public static void Main()
      {
          string str2 = "GeeksForGeeks";
          char[] dest = {'H', 'e', 'l', 'l', 'o', ' ',
                               'W', 'o', 'r', 'l', 'd' };
  
          // str index 8 to 8 + 5 has
          // to copy into Copystring
          // 5 is no of character
          // 6 is start index of Copystring
          str2.CopyTo(8, dest, 6, 5);
  
          // Displaying the result
          Console.Write("String Copied in dest is: ");
          Console.WriteLine(dest);
      }
  }
  Output:

  String Copied in dest is: Hello Geeks
  

Note: If “destination” is null then it will cause an Exception as ArgumentNullException. There are different cases when exception occurs: ArgumentOutOfRangeException

cases 1: if sourceIndex, destinationIndex, or count is negative.
cases 2: if sourceIndex does not identify a position in the current instance.
cases 3: if destinationIndex does not identify a valid index in the destination array.
cases 4: if the count is greater than the length of the substring from startIndex to the end of this instance
cases 5: if the count is greater than the length of the subarray from destinationIndex to the end of the destination array.

Reference: https://msdn.microsoft.com/en-us/library/system.string.copyto