linq query with parameter which can be empty

I have 2 important date fields in db.

startTime and goTime

I like to create custom query in which one parameter may be empty, see my example

public List<Type> GetAll( DateTime startTime, DateTime goTime )
{
List<Type> getResultBetween =

   (from i in DB.TABLENAME
    where i.startTime >= startTime 开发者_运维技巧&& i.goTime == ANYTHING
    select i).ToList();
    return getResultBetween;
}

So goal is now that I get all up to the given startTime even the goTime is not defined. It should also work if I define the goTime and let the Starttime empty. Resault should give me all till the gotime.

Thank you

Try something like this, using nullable types and building up the query explicitly:

public List<Type> GetAll(DateTime? startTime, DateTime? goTime )
{
    IQueryable<Type> query = DB.TABLENAME;
    if (startTime != null)
    {
        query = query.Where(i => i.startTime >= startTime.Value);
    }
    if (goTime != null)
    {
        query = query.Where(i => i.goTime == goTime.Value);
    }
    return query.ToList();
}

Try this "hacked" where clause:

where (i.startTime >= (startTime ?? i.startTime)) && (i.goTime >= (goTime ?? i.goTime))

For this to work, startTime and goTime should be Nullable<DateTime> (or DateTime?).

This will work in all scenarios, i.e. when...

1. Either of the parameters are null
2. Both are null
3. Both are not null

Strange it doesn't work. for more information. it's a webservice but I hope this is not the problem.

my method looks like.

public List<FDPGeschaefte> AlleGeschaefteZwischenBestimmtemDatum(string StartDatum, string EndDatum)
{
    IQueryable<FDPGeschaefte> query = DB.FDPGeschaefte;
    if (StartDatum != null && EndDatum != null)
    {
        query = query.Where(i => i.SysCreated > DateTime.Parse(StartDatum) && i.SysCreated <= DateTime.Parse(EndDatum));
    }
    if (StartDatum != null)
    {
        query = query.Where(i => i.SysCreated >= DateTime.Parse(StartDatum));
    }
    if (EndDatum != null)
    {
        query = query.Where(i => i.SysCreated <= DateTime.Parse(EndDatum));
    }
    return query.ToList();
}

if i type just one parameter in the webservice. it throws an invalid datetime argument.

Hi you could try something like this.

public static List<Type> GetAll(DateTime? startTime, DateTime? goTime)
    {
        List<Type> getResultBetween =
            (from i in DB.TableName
             where (startTime.HasValue && i.StartTime >= startTime)
                   || (goTime.HasValue && i.GoTime >= goTime)
             select i).ToList();
        return getResultBetween;
    }