StringBuilder - ExtractChar

A StringBuilder extension method that extracts the character described by @this.

public static void Main()
{
    int endIndex;

    // C# Extension Method: StringBuilder - ExtractChar
    Console.WriteLine(new StringBuilder("'a'").ExtractChar());
    Console.WriteLine(new StringBuilder("'\''").ExtractChar());
    Console.WriteLine(new StringBuilder("z'\''").ExtractChar(1, out endIndex));
    Console.WriteLine(endIndex);

    try
    {
         Console.WriteLine(new StringBuilder("'").ExtractChar());
    }
    catch (Exception ex)
    {
        Console.WriteLine("Invalid char at position: 0", ex.Message);
    }        
}

View Source

using System;
using System.Text;

public static partial class Extensions
{
    /// <summary>A StringBuilder extension method that extracts the character described by @this.</summary>
    /// <param name="this">The @this to act on.</param>
    /// <returns>The extracted character.</returns>
    public static char ExtractChar(this StringBuilder @this)
    {
        return @this.ExtractChar(0);
    }

    /// <summary>A StringBuilder extension method that extracts the character described by @this.</summary>
    /// <param name="this">The @this to act on.</param>
    /// <param name="endIndex">[out] The end index.</param>
    /// <returns>The extracted character.</returns>
    public static char ExtractChar(this StringBuilder @this, out int endIndex)
    {
        return @this.ExtractChar(0, out endIndex);
    }

    /// <summary>A StringBuilder extension method that extracts the character described by @this.</summary>
    /// <param name="this">The @this to act on.</param>
    /// <param name="startIndex">The start index.</param>
    /// <returns>The extracted character.</returns>
    public static char ExtractChar(this StringBuilder @this, int startIndex)
    {
        int endIndex;
        return @this.ExtractChar(startIndex, out endIndex);
    }

    /// <summary>A StringBuilder extension method that extracts the character described by @this.</summary>
    /// <exception cref="Exception">Thrown when an exception error condition occurs.</exception>
    /// <param name="this">The @this to act on.</param>
    /// <param name="startIndex">The start index.</param>
    /// <param name="endIndex">[out] The end index.</param>
    /// <returns>The extracted character.</returns>
    public static char ExtractChar(this StringBuilder @this, int startIndex, out int endIndex)
    {
        if (@this.Length > startIndex + 1)
        {
            var ch1 = @this[startIndex];
            var ch2 = @this[startIndex + 1];
            var ch3 = @this[startIndex + 2];

            if (ch1 == '\'' && ch3 == '\'')
            {
                endIndex = startIndex + 2;
                return ch2;
            }
        }

        throw new Exception("Invalid char at position: " + startIndex);
    }
}