c# - Custom properties and lambda expressions -

c# - Custom properties and lambda expressions -

i've added custom property linq-to-sql entity:

public partial class user { public bool isactive { { // note startdate , enddate columns of user table homecoming startdate <= datetime.now && enddate >= datetime.now; } } }

and need utilize property lambda expressions:

activeusers = users.where(u => u.isactive);

but when code executed system.notsupportedexception. exception message says "sql conversions fellow member 'user.isactive' not supported".

is there way solve problem?

the isactive show regular c# - compiled il , not available linq-to-sql (etc) inspect , turn tsql execute @ database. 1 alternative here might be:

public static expression<func<user,bool>> getisactivefilter() { homecoming user => user.startdate <= datetime.now && user.enddate >= datetime.now; }

then should able use:

activeusers = users.where(user.getisactivefilter());

or - maybe extension method:

public static iqueryable<user> activeonly(this iqueryable<user> users) { homecoming users.where(user => user.startdate <= datetime.now && user.enddate >= datetime.now); }

then:

activeusers = users.activeonly();

the difference here using iqueryable<t> interface , expression trees throughout, allows linq understand our intent, , create suitable tsql accomplish same.

c# .net linq linq-to-sql lambda