DateTime null value

Question

I ve been searching a lot but couldn t find a solution  How do you deal with a DateTime that should be able to contain an uninitialized value  equivalent to null   I have a class which might have a DateTime property value set or not  I was thinking of initializing the property holder to DateTime MinValue  which then could easily be checked  I guess this is a quite common question  how do you do that

User · Answer

You can set the DateTime to Nullable  By default DateTime is not nullable  You can make it nullable in a couple of ways  Using a question mark after the type DateTime  myTime or using the generic style Nullable   DateTime  nullDate   null    or  DateTime  nullDate

User · Answer

For normal DateTimes   if you don t initialize them at all then they will match DateTime MinValue  because it is a value type rather than a reference type   You can also use a nullable DateTime  like this   DateTime  MyNullableDate    Or the longer form   Nullable lt DateTime gt  MyNullableDate    And  finally  there s a built in way to reference the default of any type   This returns null for reference types  but for our DateTime example it will return the same as DateTime MinValue   default DateTime    or  in more recent versions of C    default

User · Answer

Following way works as well  myClass PublishDate   toPublish   DateTime Now    DateTime  null    Please note that property PublishDate should be DateTime

User · Answer

For normal DateTimes   if you don t initialize them at all then they will match DateTime MinValue  because it is a value type rather than a reference type   You can also use a nullable DateTime  like this   DateTime  MyNullableDate    Or the longer form   Nullable lt DateTime gt  MyNullableDate    And  finally  there s a built in way to reference the default of any type   This returns null for reference types  but for our DateTime example it will return the same as DateTime MinValue   default DateTime    or  in more recent versions of C    default

User · Answer

If you re using  NET 2 0  or later  you can use the nullable type   DateTime  dt   null    or    Nullable lt DateTime gt  dt   null    then later   dt   new DateTime      And you can check the value with   if  dt HasValue         Do something with dt Value     Or you can use it like   DateTime dt2   dt    DateTime MinValue    You can read more here  http   msdn microsoft com en-us library b3h38hb0 aspx

User · Answer

It is worth pointing out that  while a DateTime variable cannot be null  it still can be compared to null without a compiler error   DateTime date      if date    null      lt -- will never be  true

User · Answer

If you re using  NET 2 0  or later  you can use the nullable type   DateTime  dt   null    or    Nullable lt DateTime gt  dt   null    then later   dt   new DateTime      And you can check the value with   if  dt HasValue         Do something with dt Value     Or you can use it like   DateTime dt2   dt    DateTime MinValue    You can read more here  http   msdn microsoft com en-us library b3h38hb0 aspx

User · Answer

You can use a nullable DateTime for this   Nullable lt DateTime gt  myDateTime    or the same thing written like this   DateTime  myDateTime

User · Answer

I always set the time to DateTime MinValue  This way I do not get any NullErrorException and I can compare it to a date that I know isn t set

User · Answer

I had the same problem as I had to give Null as a parameter for DateTime while performing Unit test for Throws ArgumentNullException It worked in my case using the following option   Assert Throws lt ArgumentNullException gt      gt sut StartingDate   DateTime Parse null

User · Answer

Given the nature of a date time data type it cannot contain a null value  i e  it needs to contain a value  it cannot be blank or contain nothing  If you mark a date time variable as nullable then only can you assign a null value to it  So what you are looking to do is one of two things  there might be more but I can only think of two     Assign a minimum date time value to your variable if you don t have a value for it  You can assign a maximum date time value as well - whichever way suits you  Just make sure that you are consistent site-wide when checking your date time values  Decide on using min or max and stick with it  Mark your date time variable as nullable  This way you can set your date time variable to null if you don t have a variable to it    Let me demonstrate my first point using an example  The DateTime variable type cannot be set to null  it needs a value  in this case I am going to set it to the DateTime s minimum value if there is no value   My scenario is that I have a BlogPost class  It has many different fields properties but I chose only to use two for this example  DatePublished is when the post was published to the website and has to contain a date time value  DateModified is when a post is modified  so it doesn t have to contain a value  but can contain a value   public class BlogPost   Entity        public DateTime DateModified   get  set          public DateTime DatePublished   get  set        Using ADO NET to get the data from the database  assign DateTime MinValue is there is no value    BlogPost blogPost   new BlogPost    blogPost DateModified   sqlDataReader IsDBNull 0    DateTime MinValue   sqlDataReader GetFieldValue lt DateTime gt  0   blogPost DatePublished   sqlDataReader GetFieldValue lt DateTime gt  1     You can accomplish my second point by marking the DateModified field as nullable  Now you can set it to null if there is no value for it   public DateTime  DateModified   get  set      Using ADO NET to get the data from the database  it will look a bit different to the way it was done above  assigning null instead of DateTime MinValue    BlogPost blogPost   new BlogPost    blogPost DateModified   sqlDataReader IsDBNull 0     DateTime  null   sqlDataReader GetFieldValue lt DateTime gt  0   blogPost DatePublished   sqlDataReader GetFieldValue lt DateTime gt  1     I hope this helps to clear up any confusion  Given that my response is about 8 years later you are probably an expert C  programmer by now

User · Answer

DateTime  MyDateTime get set    MyDateTime    dr  f1      DBNull Value     DateTime  null     DateTime dr  f1

User · Answer

You can use a nullable class   DateTime  date   new DateTime

User · Answer

DateTime  MyDateTime get set    MyDateTime    dr  f1      DBNull Value     DateTime  null     DateTime dr  f1

User · Answer

If you re using  NET 2 0  or later  you can use the nullable type   DateTime  dt   null    or    Nullable lt DateTime gt  dt   null    then later   dt   new DateTime      And you can check the value with   if  dt HasValue         Do something with dt Value     Or you can use it like   DateTime dt2   dt    DateTime MinValue    You can read more here  http   msdn microsoft com en-us library b3h38hb0 aspx

User · Answer

It is worth pointing out that  while a DateTime variable cannot be null  it still can be compared to null without a compiler error   DateTime date      if date    null      lt -- will never be  true

User · Answer

I d consider using a nullable types   DateTime  myDate instead of DateTime myDate

User · Answer

If you are  sometimes  expecting null you could use something like this   var orderResults   Repository GetOrders id   DateTime  model DateFrom   DateTime  model DateTo    In your repository use null-able datetime   public Orders   GetOrders string id  DateTime  dateFrom  DateTime  dateTo

User · Answer

Just be warned - When using a Nullable its obviously no longer a  pure  datetime object  as such you cannot access the DateTime members directly  I ll try and explain   By using Nullable lt   you re basically wrapping DateTime in a container  thank you generics  of which is nullable - obviously its purpose  This container has its own properties which you can call that will provide access to the aforementioned DateTime object  after using the correct property - in this case Nullable Value - you then have access to the standard DateTime members  properties etc   So - now the issue comes to mind as to the best way to access the DateTime object  There are a few ways  number 1 is by FAR the best and 2 is  dude why     Using the Nullable Value property   DateTime date   myNullableObject Value ToUniversalTime      Works  DateTime date   myNullableObject ToUniversalTime      Not a datetime object  fails Converting the nullable object to datetime using Convert ToDateTime     DateTime date   Convert ToDateTime myNullableObject  ToUniversalTime      works but why      Although the answer is well documented at this point  I believe the usage of Nullable was probably worth posting about  Sorry if you disagree   edit  Removed a third option as it was a bit overly specific and case dependent

User · Answer

You can set the DateTime to Nullable  By default DateTime is not nullable  You can make it nullable in a couple of ways  Using a question mark after the type DateTime  myTime or using the generic style Nullable   DateTime  nullDate   null    or  DateTime  nullDate

User · Answer

Following way works as well  myClass PublishDate   toPublish   DateTime Now    DateTime  null    Please note that property PublishDate should be DateTime

User · Answer

You can set the DateTime to Nullable  By default DateTime is not nullable  You can make it nullable in a couple of ways  Using a question mark after the type DateTime  myTime or using the generic style Nullable   DateTime  nullDate   null    or  DateTime  nullDate

User · Answer

You can use a nullable class   DateTime  date   new DateTime

User · Answer

You can use a nullable class   DateTime  date   new DateTime

User · Answer

If you are  sometimes  expecting null you could use something like this   var orderResults   Repository GetOrders id   DateTime  model DateFrom   DateTime  model DateTo    In your repository use null-able datetime   public Orders   GetOrders string id  DateTime  dateFrom  DateTime  dateTo

User · Answer

I always set the time to DateTime MinValue  This way I do not get any NullErrorException and I can compare it to a date that I know isn t set

User · Answer

I always set the time to DateTime MinValue  This way I do not get any NullErrorException and I can compare it to a date that I know isn t set

User · Answer

You can use a nullable class   DateTime  date   new DateTime

User · Answer

I had the same problem as I had to give Null as a parameter for DateTime while performing Unit test for Throws ArgumentNullException It worked in my case using the following option   Assert Throws lt ArgumentNullException gt      gt sut StartingDate   DateTime Parse null

User · Answer

Just be warned - When using a Nullable its obviously no longer a  pure  datetime object  as such you cannot access the DateTime members directly  I ll try and explain   By using Nullable lt   you re basically wrapping DateTime in a container  thank you generics  of which is nullable - obviously its purpose  This container has its own properties which you can call that will provide access to the aforementioned DateTime object  after using the correct property - in this case Nullable Value - you then have access to the standard DateTime members  properties etc   So - now the issue comes to mind as to the best way to access the DateTime object  There are a few ways  number 1 is by FAR the best and 2 is  dude why     Using the Nullable Value property   DateTime date   myNullableObject Value ToUniversalTime      Works  DateTime date   myNullableObject ToUniversalTime      Not a datetime object  fails Converting the nullable object to datetime using Convert ToDateTime     DateTime date   Convert ToDateTime myNullableObject  ToUniversalTime      works but why      Although the answer is well documented at this point  I believe the usage of Nullable was probably worth posting about  Sorry if you disagree   edit  Removed a third option as it was a bit overly specific and case dependent

User · Answer

Given the nature of a date time data type it cannot contain a null value  i e  it needs to contain a value  it cannot be blank or contain nothing  If you mark a date time variable as nullable then only can you assign a null value to it  So what you are looking to do is one of two things  there might be more but I can only think of two     Assign a minimum date time value to your variable if you don t have a value for it  You can assign a maximum date time value as well - whichever way suits you  Just make sure that you are consistent site-wide when checking your date time values  Decide on using min or max and stick with it  Mark your date time variable as nullable  This way you can set your date time variable to null if you don t have a variable to it    Let me demonstrate my first point using an example  The DateTime variable type cannot be set to null  it needs a value  in this case I am going to set it to the DateTime s minimum value if there is no value   My scenario is that I have a BlogPost class  It has many different fields properties but I chose only to use two for this example  DatePublished is when the post was published to the website and has to contain a date time value  DateModified is when a post is modified  so it doesn t have to contain a value  but can contain a value   public class BlogPost   Entity        public DateTime DateModified   get  set          public DateTime DatePublished   get  set        Using ADO NET to get the data from the database  assign DateTime MinValue is there is no value    BlogPost blogPost   new BlogPost    blogPost DateModified   sqlDataReader IsDBNull 0    DateTime MinValue   sqlDataReader GetFieldValue lt DateTime gt  0   blogPost DatePublished   sqlDataReader GetFieldValue lt DateTime gt  1     You can accomplish my second point by marking the DateModified field as nullable  Now you can set it to null if there is no value for it   public DateTime  DateModified   get  set      Using ADO NET to get the data from the database  it will look a bit different to the way it was done above  assigning null instead of DateTime MinValue    BlogPost blogPost   new BlogPost    blogPost DateModified   sqlDataReader IsDBNull 0     DateTime  null   sqlDataReader GetFieldValue lt DateTime gt  0   blogPost DatePublished   sqlDataReader GetFieldValue lt DateTime gt  1     I hope this helps to clear up any confusion  Given that my response is about 8 years later you are probably an expert C  programmer by now

User · Answer

You can use a nullable DateTime for this   Nullable lt DateTime gt  myDateTime    or the same thing written like this   DateTime  myDateTime

User · Answer

I d consider using a nullable types   DateTime  myDate instead of DateTime myDate

User · Answer

I always set the time to DateTime MinValue  This way I do not get any NullErrorException and I can compare it to a date that I know isn t set

User · Answer

Although everyone has already given you the answer   I ll mention a way which makes it easy to pass a datetime into a function   ERROR cannot convert system datetime  to system datetime   DateTime  dt   null  DateTime dte   Convert ToDateTime dt     Now you may pass dte inside the function without any issues

User · Answer

I d consider using a nullable types   DateTime  myDate instead of DateTime myDate

User · Answer

For normal DateTimes   if you don t initialize them at all then they will match DateTime MinValue  because it is a value type rather than a reference type   You can also use a nullable DateTime  like this   DateTime  MyNullableDate    Or the longer form   Nullable lt DateTime gt  MyNullableDate    And  finally  there s a built in way to reference the default of any type   This returns null for reference types  but for our DateTime example it will return the same as DateTime MinValue   default DateTime    or  in more recent versions of C    default

User · Answer

You can set the DateTime to Nullable  By default DateTime is not nullable  You can make it nullable in a couple of ways  Using a question mark after the type DateTime  myTime or using the generic style Nullable   DateTime  nullDate   null    or  DateTime  nullDate

User · Answer

For normal DateTimes   if you don t initialize them at all then they will match DateTime MinValue  because it is a value type rather than a reference type   You can also use a nullable DateTime  like this   DateTime  MyNullableDate    Or the longer form   Nullable lt DateTime gt  MyNullableDate    And  finally  there s a built in way to reference the default of any type   This returns null for reference types  but for our DateTime example it will return the same as DateTime MinValue   default DateTime    or  in more recent versions of C    default

User · Answer

Although everyone has already given you the answer   I ll mention a way which makes it easy to pass a datetime into a function   ERROR cannot convert system datetime  to system datetime   DateTime  dt   null  DateTime dte   Convert ToDateTime dt     Now you may pass dte inside the function without any issues

User · Answer

I d consider using a nullable types   DateTime  myDate instead of DateTime myDate

User · Answer

If you re using  NET 2 0  or later  you can use the nullable type   DateTime  dt   null    or    Nullable lt DateTime gt  dt   null    then later   dt   new DateTime      And you can check the value with   if  dt HasValue         Do something with dt Value     Or you can use it like   DateTime dt2   dt    DateTime MinValue    You can read more here  http   msdn microsoft com en-us library b3h38hb0 aspx

User · Answer

You can use a nullable DateTime for this   Nullable lt DateTime gt  myDateTime    or the same thing written like this   DateTime  myDateTime

User · Answer

You can use a nullable DateTime for this   Nullable lt DateTime gt  myDateTime    or the same thing written like this   DateTime  myDateTime

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