Sample immutable struct that shows how to override Equals and GetHashCode, as well as the == and != operators

SampleStruct.cs

/// <summary>
/// Sample struct that shows how to override GetHashCode and Equals, as well as the == and != 
/// operators.
/// </summary>
/// <remarks>
/// This type is immutable.
/// </remarks>
public struct SampleStruct
{
    #region Private Backing Fields

    private readonly DateTime _startDate;
    private readonly DateTime _endDate;

    #endregion


    #region Public Properties

    public DateTime StartDate { get { return this._startDate; } }
    public DateTime EndDate { get { return this._endDate; } }

    #endregion


    #region Constructors

    public SampleStruct(DateTime startDate, DateTime endDate)
        : this()
    {
        this._startDate = startDate;
        this._endDate = endDate;
    }

    #endregion


    #region Override Methods

    public override string ToString()
    {
        return string.Format("{0} - {1}", this.StartDate, this.EndDate);
    }

    public override int GetHashCode()
    {
        // Overflow is fine, just wrap
        unchecked
        {
            int hash = 17;

            hash = hash * 23 + this.StartDate.GetHashCode();
            hash = hash * 23 + this.EndDate.GetHashCode();

            return hash;
        }
    }

    public override bool Equals(object obj)
    {
        if (object.ReferenceEquals(null, obj))
        {
            return false;
        }

        if (object.ReferenceEquals(this, obj))
        {
            return true;
        }

        if (obj.GetType() != typeof(SampleStruct))
        {
            return false;
        }

        return this.Equals((SampleStruct)obj);
    }

    public bool Equals(SampleStruct other)
    {
        if (object.ReferenceEquals(null, other))
        {
            return false;
        }

        if (object.ReferenceEquals(this, other))
        {
            return true;
        }

        return this.StartDate == other.StartDate
            && this.EndDate == other.EndDate;
    }

    public static bool operator ==(SampleStruct left, SampleStruct right)
    {
        return object.Equals(left, right);
    }

    public static bool operator !=(SampleStruct left, SampleStruct right)
    {
        return !object.Equals(left, right);
    }

    #endregion
}

TestProgram.cs

class Program
{
    static void Main(string[] args)
    {
        var now = DateTime.Now;
        var s1 = new SampleStruct(now, now.AddDays(1.0));
        var s2 = new SampleStruct(now, now.AddDays(1.0));

        Console.WriteLine("s1 == s1: {0}", s1 == s1);
        Console.WriteLine("s1 == s2: {0}", s1 == s2);
        Console.WriteLine("s2 == s1: {0}", s2 == s1);
        Console.WriteLine("s2 == s2: {0}", s2 == s2);

        Console.WriteLine();

        Console.WriteLine("s1 != s1: {0}", s1 != s1);
        Console.WriteLine("s1 != s2: {0}", s1 != s2);
        Console.WriteLine("s2 != s1: {0}", s2 != s1);
        Console.WriteLine("s2 != s2: {0}", s2 != s2);

        Console.WriteLine();

        Console.WriteLine("s1.Equals(s1): {0}", s1.Equals(s1));
        Console.WriteLine("s1.Equals(s2): {0}", s1.Equals(s2));
        Console.WriteLine("s2.Equals(s1): {0}", s2.Equals(s1));
        Console.WriteLine("s2.Equals(s2): {0}", s2.Equals(s2));

        Console.WriteLine();

        Console.WriteLine("!s1.Equals(s1): {0}", !s1.Equals(s1));
        Console.WriteLine("!s1.Equals(s2): {0}", !s1.Equals(s2));
        Console.WriteLine("!s2.Equals(s1): {0}", !s2.Equals(s1));
        Console.WriteLine("!s2.Equals(s2): {0}", !s2.Equals(s2));

        Console.WriteLine();

        Console.WriteLine("object.ReferenceEquals(s1, s1): {0}", object.ReferenceEquals(s1, s1));
        Console.WriteLine("object.ReferenceEquals(s1, s2): {0}", object.ReferenceEquals(s1, s2));
        Console.WriteLine("object.ReferenceEquals(s2, s1): {0}", object.ReferenceEquals(s2, s1));
        Console.WriteLine("object.ReferenceEquals(s2, s2): {0}", object.ReferenceEquals(s2, s2));

        Console.WriteLine();

        Console.WriteLine("!object.ReferenceEquals(s1, s1): {0}", !object.ReferenceEquals(s1, s1));
        Console.WriteLine("!object.ReferenceEquals(s1, s2): {0}", !object.ReferenceEquals(s1, s2));
        Console.WriteLine("!object.ReferenceEquals(s2, s1): {0}", !object.ReferenceEquals(s2, s1));
        Console.WriteLine("!object.ReferenceEquals(s2, s2): {0}", !object.ReferenceEquals(s2, s2));

        Console.WriteLine("Press ENTER to quit...");
        Console.ReadLine();
    }
}
/* Output:
s1 == s1: True
s1 == s2: True
s2 == s1: True
s2 == s2: True

s1 != s1: False
s1 != s2: False
s2 != s1: False
s2 != s2: False

s1.Equals(s1): True
s1.Equals(s2): True
s2.Equals(s1): True
s2.Equals(s2): True

!s1.Equals(s1): False
!s1.Equals(s2): False
!s2.Equals(s1): False
!s2.Equals(s2): False

object.ReferenceEquals(s1, s1): False
object.ReferenceEquals(s1, s2): False
object.ReferenceEquals(s2, s1): False
object.ReferenceEquals(s2, s2): False

!object.ReferenceEquals(s1, s1): True
!object.ReferenceEquals(s1, s2): True
!object.ReferenceEquals(s2, s1): True
!object.ReferenceEquals(s2, s2): True
Press ENTER to quit...
*/

I should note that some of this code comes from various places:

• ReSharper
• A Jon Skeet answer on Stack Overflow