how can i remove the value from a DateTime?

i have an existing DateTime? object that has a datetime in i开发者_开发技巧t. I want to remove the datetime value from it so when you ask "HasValue" it returns false?

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Nullable<T>is immutable, so you will have to reassign the variable to a different value to be able to change / remove the underlying value. This makes sense since it is a value-type (although a special one at that); value-types are normally immutable in the framework. You will notice that neither theValuenor theHasValue property forNullable<T>has a setter.

DateTime? nullableDt = DateTime.Now; 
Console.WriteLine(nullableDt.HasValue); //true

nullableDt = null; 
Console.WriteLine(nullableDt.HasValue); //false

or

nullableDt = new DateTime?();

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Set it to null.

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If you have

DateTime? value = DateTime.Now;

then call

value = null;

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Why not just set it back to null?

  DateTime? d = null;

  System.Diagnostics.Debug.WriteLine("HasValue1 = {0}", d.HasValue); //False

  d = DateTime.Now;

  System.Diagnostics.Debug.WriteLine("HasValue2 = {0}", d.HasValue); //True

  d = null;

  System.Diagnostics.Debug.WriteLine("HasValue3 = {0}", d.HasValue); //False

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The variable itself cannot be null, though you can set the minValue, it is an equivalent to '1/1/0001 00:00:00'

DateTime dvar = DateTime.MinValue;