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c#
group:set a DateTime to NULL
c#:
//First I check to see if anything is in this datarow column, because sometimes we have no data. DateTime dt; if ( datarow["date"].ToString().Length > 0) { //We assume the data is a date dt = (DateTime)datarow["date"]; } else //We have no data in this column { dt = DBNull.Value; //this does not work } Then I set the param. cmdUpdate.Parameters.Add("@invoicedate", SqlDbType.NVarChar, 40).Value = dt.ToShortDateString(); If there is a date in 'datarow["date"]' everything works fine, but if there is no data it throws an exception. So I set up the if statement to check for something in that column, if there is something I assume it's a date and assign it to dt. But if there no data I want to asign nothing to dt. Thanks Paul
I also had to use an if statement. I actually wrote a function to do it
for me. I know there has to be a a cleaner way but i couldnt find one. Heres mine: private object returnNullIfBlank(object s) { if (s==null | s.ToString()=="" | s == (object) System.DateTime.MinValue) return System.Data.SqlTypes.SqlString.Null; //return System.Data.SqlTypes.SqlDateTime.Null; else return s; } so you might want a line like this: dt=System.Data.SqlTypes.SqlDateTime.Null unlikely put you may possibly want this as a last resort: (CAST_ME) System.Data.SqlTypes.SqlString.Null -Dwight http://logical4.com
..NET 1.1 atleast does not support nullable value types. Even with .NET 2.0,
nullable value types donot fully solve this problem. You have to use the DBNull structure to get around this issue as Jon explained. - Sahil Malik http://codebetter.com/blogs/sahil.malik/ [quoted text, click to view] <Paulb1us@newsgroup.nospam> wrote in message news:DF21646B-3C23-4F13-9E31-186AD080200E@microsoft.com... >I want to set a DateTime field to Null before passing it to the DB > > //First I check to see if anything is in this datarow column, because > sometimes we have no data. > DateTime dt; > if ( datarow["date"].ToString().Length > 0) > { > //We assume the data is a date > dt = (DateTime)datarow["date"]; > } > else > //We have no data in this column > { > dt = DBNull.Value; //this does not work > } > > Then I set the param. > > cmdUpdate.Parameters.Add("@invoicedate", SqlDbType.NVarChar, 40).Value = > dt.ToShortDateString(); > > If there is a date in 'datarow["date"]' everything works fine, but if > there > is no data it throws an exception. So I set up the if statement to check > for > something in that column, if there is something I assume it's a date and > assign it to dt. But if there no data I want to asign nothing to dt. > > Thanks > > Paul > >
[quoted text, click to view]
Paulb1us@newsgroup.nospam <Paulb1us@newsgroup.nospam> wrote: > I want to set a DateTime field to Null before passing it to the DB You just can't do that. A DateTime can't be null. It can't be DBNull.Value, either (which is something different). [quoted text, click to view] > //First I check to see if anything is in this datarow column, because > sometimes we have no data. > DateTime dt; > if ( datarow["date"].ToString().Length > 0) > { > //We assume the data is a date > dt = (DateTime)datarow["date"]; > } > else > //We have no data in this column > { > dt = DBNull.Value; //this does not work > } > > Then I set the param. > > cmdUpdate.Parameters.Add("@invoicedate", SqlDbType.NVarChar, 40).Value = > dt.ToShortDateString(); Yikes - is the field in the database really a string rather than a date-related type? That's nasty. [quoted text, click to view] > If there is a date in 'datarow["date"]' everything works fine, but if there > is no data it throws an exception. So I set up the if statement to check for > something in that column, if there is something I assume it's a date and > assign it to dt. But if there no data I want to asign nothing to dt. You can't do that. What you can do is: object parameterValue; if (!datarow.IsNull("date")) { parameterValue = ((DateTime)datarow["date"]).ToShortDateString(); } else { parameterValue = DBNull.Value; } cmdUpdate.Parameters.Add ("@invoicedate", SqlDbType.NVarChar, parameterValue); -- Jon Skeet - <skeet@pobox.com> http://www.pobox.com/~skeet
Thank you Jon,
That works just fine. I know the DB field should be Date and not string but in this certain instance it needs to be a string. Thank you for your help. Paul [quoted text, click to view] "Jon Skeet [C# MVP]" wrote:
> Paulb1us@newsgroup.nospam <Paulb1us@newsgroup.nospam> wrote: > > I want to set a DateTime field to Null before passing it to the DB > > You just can't do that. A DateTime can't be null. It can't be > DBNull.Value, either (which is something different). > > > //First I check to see if anything is in this datarow column, because > > sometimes we have no data. > > DateTime dt; > > if ( datarow["date"].ToString().Length > 0) > > { > > //We assume the data is a date > > dt = (DateTime)datarow["date"]; > > } > > else > > //We have no data in this column > > { > > dt = DBNull.Value; //this does not work > > } > > > > Then I set the param. > > > > cmdUpdate.Parameters.Add("@invoicedate", SqlDbType.NVarChar, 40).Value = > > dt.ToShortDateString(); > > Yikes - is the field in the database really a string rather than a > date-related type? That's nasty. > > > If there is a date in 'datarow["date"]' everything works fine, but if there > > is no data it throws an exception. So I set up the if statement to check for > > something in that column, if there is something I assume it's a date and > > assign it to dt. But if there no data I want to asign nothing to dt. > > You can't do that. What you can do is: > > object parameterValue; > > if (!datarow.IsNull("date")) > { > parameterValue = ((DateTime)datarow["date"]).ToShortDateString(); > } > else > { > parameterValue = DBNull.Value; > } > cmdUpdate.Parameters.Add ("@invoicedate", SqlDbType.NVarChar, > parameterValue); > > -- > Jon Skeet - <skeet@pobox.com> > http://www.pobox.com/~skeet > If replying to the group, please do not mail me too
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> You just can't do that. A DateTime can't be null. It can't be > DBNull.Value, either (which is something different). yea , and just to confirm that it is because that value types cant be null and they are always initialized to there respective default values, unless they accept a constructor for custom initial values. Right? Ab. [quoted text, click to view] "Jon Skeet [C# MVP]" <skeet@pobox.com> wrote in message news:MPG.1c693e6aa69333398bcc5@msnews.microsoft.com... > Paulb1us@newsgroup.nospam <Paulb1us@newsgroup.nospam> wrote: > > I want to set a DateTime field to Null before passing it to the DB > > You just can't do that. A DateTime can't be null. It can't be > DBNull.Value, either (which is something different). > > > //First I check to see if anything is in this datarow column, because > > sometimes we have no data. > > DateTime dt; > > if ( datarow["date"].ToString().Length > 0) > > { > > //We assume the data is a date > > dt = (DateTime)datarow["date"]; > > } > > else > > //We have no data in this column > > { > > dt = DBNull.Value; //this does not work > > } > > > > Then I set the param. > > > > cmdUpdate.Parameters.Add("@invoicedate", SqlDbType.NVarChar, 40).Value = > > dt.ToShortDateString(); > > Yikes - is the field in the database really a string rather than a > date-related type? That's nasty. > > > If there is a date in 'datarow["date"]' everything works fine, but if there > > is no data it throws an exception. So I set up the if statement to check for > > something in that column, if there is something I assume it's a date and > > assign it to dt. But if there no data I want to asign nothing to dt. > > You can't do that. What you can do is: > > object parameterValue; > > if (!datarow.IsNull("date")) > { > parameterValue = ((DateTime)datarow["date"]).ToShortDateString(); > } > else > { > parameterValue = DBNull.Value; > } > cmdUpdate.Parameters.Add ("@invoicedate", SqlDbType.NVarChar, > parameterValue); > > -- > Jon Skeet - <skeet@pobox.com> > http://www.pobox.com/~skeet > If replying to the group, please do not mail me too
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Abubakar <emailallrise@yahoo.com> wrote: > > You just can't do that. A DateTime can't be null. It can't be > > DBNull.Value, either (which is something different). > > yea , and just to confirm that it is because that value types cant be null > and they are always initialized to there respective default values, unless > they accept a constructor for custom initial values. Right? It's not really due to custom initial values - it's because null is a reference, and the value of a value type isn't a reference, so can't be null. -- Jon Skeet - <skeet@pobox.com> http://www.pobox.com/~skeet
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