public static bool Equals(NullableDateTime x, NullableDateTime y)
{
if (x.HasValue != y.HasValue) //one is null
{
return(false);
}
else if (x.HasValue) //therefor y also HasValue
{
return(x.Value == y.Value);
}
else //both are null
{
return(true);
}
}
public int CompareTo(object obj)
{
if (obj is NullableDateTime) //chack and unbox
{
NullableDateTime value = (NullableDateTime)obj;
if (value.HasValue == this.HasValue) //both null or not null
{
if (this.HasValue) //this has a value, so they both do
{
return(Value.CompareTo(value.Value));
}
else
{
return(0); //both null, so they are equal;
}
}
else //one is null
{
if (HasValue) //he have a value, so we are greater.
{
return(1);
}
else
{
return(-1);
}
}
}
else if (obj is DateTime)
{
DateTime value = (DateTime)obj;
if (HasValue) //not null, so compare the real values.
{
return(Value.CompareTo(value));
}
else
{
return(-1); //this is null, so less that the real value;
}
}
throw new ArgumentException("NullableDateTime can only compare to another NullableDateTime or a System.DateTime");
}
public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value,
Type destinationType)
{
if (destinationType == typeof(InstanceDescriptor) && value is NullableDateTime)
{
NullableDateTime nullable = (NullableDateTime)value;
Type[] constructorArgTypes = new Type[1] {
typeof(DateTime)
};
ConstructorInfo constructor = typeof(NullableDateTime).GetConstructor(constructorArgTypes);
if (constructor != null)
{
object[] constructorArgValues = new object[1] {
nullable.Value
};
return(new InstanceDescriptor(constructor, constructorArgValues));
}
}
else if (destinationType == typeof(DateTime))
{
NullableDateTime ndt = (NullableDateTime)value;
if (ndt.HasValue)
{
return(ndt.Value);
}
else
{
return(DBNull.Value);
}
}
return(base.ConvertTo(context, culture, value, destinationType));
}
public bool Equals(NullableDateTime x)
{
return(Equals(this, x));
}