Casting null values

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  • Microsoft Newsserver
    #1

    Casting null values

    Hi,

    Im having a bit of difficulty working out how to do the following.


    method ( paramType? param1, DateTime? requiredByDate , paramType? param3)


    I have a row property which I need to pass to this method, this has a
    property of IsNull which is a boolean, so I tried to do the following

    method ( param1,
    row.IsRequiredB yDateNull() ? null, row.RequiredByD ate,
    param3 )

    This fails on compile because it cant cast from a null to a DateTime.

    How can i construct this ?


    Tags: None
    • Jon Skeet [C# MVP]
      #2
      Re: Casting null values

      Microsoft Newsserver <me@nowhere.com wrote:
      Im having a bit of difficulty working out how to do the following.
      >
      >
      method ( paramType? param1, DateTime? requiredByDate , paramType? param3)
      >
      >
      I have a row property which I need to pass to this method, this has a
      property of IsNull which is a boolean, so I tried to do the following
      >
      method ( param1,
      row.IsRequiredB yDateNull() ? null, row.RequiredByD ate,
      param3 )
      >
      This fails on compile because it cant cast from a null to a DateTime.
      >
      How can i construct this ?
      Don't cast to DateTime - cast to DateTime? (with the question mark).
      Then it should be fine.

      --
      Jon Skeet - <skeet@pobox.co m>
      Web site: http://www.pobox.com/~skeet
      Blog: http://www.msmvps.com/jon_skeet
      C# in Depth: http://csharpindepth.com

        Comment

        • Microsoft Newsserver
          #3
          Re: Casting null values


          should have read

          row.IsRequiredB yDateNull() ? null : row.RequiredByD ate;





          "Microsoft Newsserver" <me@nowhere.com wrote in message
          news:eVYNxNU1IH A.4704@TK2MSFTN GP05.phx.gbl...
          Hi,
          >
          Im having a bit of difficulty working out how to do the following.
          >
          >
          method ( paramType? param1, DateTime? requiredByDate , paramType?
          param3)
          >
          >
          I have a row property which I need to pass to this method, this has a
          property of IsNull which is a boolean, so I tried to do the following
          >
          method ( param1,
          row.IsRequiredB yDateNull() ? null, row.RequiredByD ate,
          param3 )
          >
          This fails on compile because it cant cast from a null to a DateTime.
          >
          How can i construct this ?
          >

            Comment

            • Microsoft Newsserver
              #4
              Re: Casting null values

              Great thanks Jon


              "Jon Skeet [C# MVP]" <skeet@pobox.co mwrote in message
              news:MPG.22c9ce 55cd3129f2daf@m snews.microsoft .com...
              Microsoft Newsserver <me@nowhere.com wrote:
              >Im having a bit of difficulty working out how to do the following.
              >>
              >>
              >method ( paramType? param1, DateTime? requiredByDate , paramType?
              >param3)
              >>
              >>
              >I have a row property which I need to pass to this method, this has a
              >property of IsNull which is a boolean, so I tried to do the following
              >>
              >method ( param1,
              > row.IsRequiredB yDateNull() ? null,
              >row.RequiredBy Date,
              > param3 )
              >>
              >This fails on compile because it cant cast from a null to a DateTime.
              >>
              >How can i construct this ?
              >
              Don't cast to DateTime - cast to DateTime? (with the question mark).
              Then it should be fine.
              >
              --
              Jon Skeet - <skeet@pobox.co m>
              Web site: http://www.pobox.com/~skeet
              Blog: http://www.msmvps.com/jon_skeet
              C# in Depth: http://csharpindepth.com

                Comment

                • =?ISO-8859-2?Q?Micha=B3_Piaskowski?=
                  #5
                  Re: Casting null values

                  On Jun 23, 5:16 pm, "Microsoft Newsserver" <m...@nowhere.c omwrote:
                  should have read
                  >
                  row.IsRequiredB yDateNull() ? null : row.RequiredByD ate;
                  >
                  "Microsoft Newsserver" <m...@nowhere.c omwrote in message
                  >
                  news:eVYNxNU1IH A.4704@TK2MSFTN GP05.phx.gbl...
                  >
                  Hi,
                  >
                  Im having a bit of difficulty working out how to do the following.
                  >
                  method ( paramType? param1, DateTime? requiredByDate , paramType?
                  param3)
                  >
                  I have a row property which I need to pass to this method, this has a
                  property of IsNull which is a boolean, so I tried to do the following
                  >
                  method ( param1,
                  row.IsRequiredB yDateNull() ? null, row.RequiredByD ate,
                  param3 )
                  >
                  This fails on compile because it cant cast from a null to a DateTime.
                  >
                  How can i construct this ?
                  I once had the same problem.
                  I can't check it with a compiler right now, but the solution is
                  something like this:

                  row.IsRequiredB yDateNull() ? (DateTime?)null : row.RequiredByD ate;

                    Comment

                    • Microsoft Newsserver
                      #6
                      Re: Casting null values

                      yes, your absolutely correct. In fact Jon Skeet came up with the same
                      solution. For some reason , I never thought of casting to a nullable type.
                      DOH!

                      Thanks for your help.


                      "Michal Piaskowski" <piaskal@gmail. comwrote in message
                      news:ac8445c2-574a-4cd2-a27e-addabad89dff@d4 5g2000hsc.googl egroups.com...
                      On Jun 23, 5:16 pm, "Microsoft Newsserver" <m...@nowhere.c omwrote:
                      >should have read
                      >>
                      >row.IsRequired ByDateNull() ? null : row.RequiredByD ate;
                      >>
                      >"Microsoft Newsserver" <m...@nowhere.c omwrote in message
                      >>
                      >news:eVYNxNU1I HA.4704@TK2MSFT NGP05.phx.gbl.. .
                      >>
                      Hi,
                      >>
                      Im having a bit of difficulty working out how to do the following.
                      >>
                      method ( paramType? param1, DateTime? requiredByDate , paramType?
                      param3)
                      >>
                      I have a row property which I need to pass to this method, this has a
                      property of IsNull which is a boolean, so I tried to do the following
                      >>
                      method ( param1,
                      row.IsRequiredB yDateNull() ? null,
                      row.RequiredByD ate,
                      param3 )
                      >>
                      This fails on compile because it cant cast from a null to a DateTime.
                      >>
                      How can i construct this ?
                      >
                      I once had the same problem.
                      I can't check it with a compiler right now, but the solution is
                      something like this:
                      >
                      row.IsRequiredB yDateNull() ? (DateTime?)null : row.RequiredByD ate;

                        Comment

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