Char - IsSurrogate

Indicates whether the specified character has a surrogate code unit.

Try it

public static void Main()
{
    char [] input = new char[] { 'a', '\uD800', '\uDC00', 'z' };

    Console.WriteLine("Is each of the following characters a high surrogate?");
	
    for (int i = 0; i < input.Length; i++)
    {
		// C# Extension Method: Char - IsSurrogate
		var result = input[i].IsSurrogate();
		
        Console.WriteLine("input[{0}] = {1} ", i, result);
    }
}

View Source 
using System;

public static partial class Extensions
{
    /// <summary>
    ///     Indicates whether the specified character has a surrogate code unit.
    /// </summary>
    /// <param name="c">The Unicode character to evaluate.</param>
    /// <returns>true if  is either a high surrogate or a low surrogate; otherwise, false.</returns>
    public static Boolean IsSurrogate(this Char c)
    {
        return Char.IsSurrogate(c);
    }
}