当相同类型的两个对象具有相同的值时，为什么哈希码不同?

我的理解是，GetHashCode将为共享相同值的两个不同实例返回相同的值。MSDN文档在这一点上有点模糊。

哈希码是一个用于标识对象的数值在相等性测试期间。

如果我有两个相同类型和相同值的实例，GetHashCode()会返回相同的值吗?

假设所有的值都是相同的，下面的测试是通过还是失败?

SecurityUser只有getter和setter;

    [TestMethod]
    public void GetHashCode_Equal_Test()
    {
        SecurityUser objA = new SecurityUser(EmployeeName, EmployeeNumber, LastLogOnDate, Status, UserName);
        SecurityUser objB = new SecurityUser(EmployeeName, EmployeeNumber, LastLogOnDate, Status, UserName);
        int hashcodeA = objA.GetHashCode();
        int hashcodeB = objB.GetHashCode();
        Assert.AreEqual<int>(hashcodeA, hashcodeB);
    }

/// <summary>
/// This class represents a SecurityUser entity in AppSecurity.
/// </summary>
public sealed class SecurityUser
{
    #region [Constructor]
    /// <summary>
    /// Initializes a new instance of the <see cref="SecurityUser"/> class using the
    /// parameters passed.
    /// </summary>
    /// <param name="employeeName">The employee name to initialize with.</param>
    /// <param name="employeeNumber">The employee id number to initialize with.</param>
    /// <param name="lastLogOnDate">The last logon date to initialize with.</param>
    /// <param name="status">The <see cref="SecurityStatus"/> to initialize with.</param>
    /// <param name="userName">The userName to initialize with.</param>        
    public SecurityUser(
        string employeeName,
        int employeeNumber,            
        DateTime? lastLogOnDate,
        SecurityStatus status,
        string userName)
    {
        if (employeeName == null)
            throw new ArgumentNullException("employeeName");
        if (userName == null)
            throw new ArgumentNullException("userName");
        this.EmployeeName = employeeName;
        this.EmployeeNumber = employeeNumber;
        this.LastLogOnDate = lastLogOnDate;
        this.Status = status;
        this.UserName = userName;
    }
    #endregion
    #region [Properties]
    /// <summary>
    /// Gets the employee name of the current instance.
    /// </summary>
    public string EmployeeName { get; private set; }
    /// <summary>
    /// Gets the employee id number of the current instance.
    /// </summary>
    public int EmployeeNumber { get; private set; }
    /// <summary>
    /// Gets the last logon date of the current instance.
    /// </summary>
    public DateTime? LastLogOnDate { get; private set; }
    /// <summary>
    /// Gets the userName of the current instance.
    /// </summary>
    public string UserName { get; private set; }
    /// <summary>
    /// Gets the <see cref="SecurityStatus"/> of the current instance.
    /// </summary>
    public SecurityStatus Status { get; private set; }
    #endregion
}