C# String CopyTo() Method

In C#, the CopyTo() is a method of String Class. 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 an array of Unicode characters.

Example 1: Using the CopyTo() method to copy characters from a string to a character array.

// C# program to illustrate the
// String.CopyTo() Method
// Method
using System;

class Geeks
{
	public static void Main()
	{
		// Creating a string
		string s = "GeeksForGeeks";

		// Destination char array
		char[] dest = new char[3];

		//Copying 3 characters from the 5th index 
		//of the string to the destination char array.
		s.CopyTo(5, dest, 0, 3);
        
		// Displaying the copied string
		Console.WriteLine($"The Copied String is: {new string(dest)}");
	}
}

The Copied String is: For

Syntax of String CopyTo() Method

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

Parameters:

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

Exceptions:

• ArgumentNullException: If the destination array is null then it will throw this Exception.
• ArgumentOutOfRangeException: There are different cases when an exception occurs
  • If sourceIndex, destinationIndex, or count is negative.
  • If sourceIndex does not identify a position in the current instance.
  • If destinationIndex does not identify a valid index in the destination array.
  • If the count is greater than the length of the substring from startIndex to the end of this instance
  • If the count is greater than the length of the subarray from destinationIndex to the end of the destination array.

Example 2: Using the CopyTo() method to modify an existing character array.

// C# program to illustrate the 
// ToCopy() string method 
using System; 

class Geeks 
{ 

	public static void Main() 
	{ 
		string s = "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 
		s.CopyTo(8, dest, 6, 5); 
		
		// Displaying the result 
		Console.Write("String Copied in dest is: "); 
		Console.WriteLine(dest); 
	} 
}