Hi I have two predicates. And I wonder if it is possible to join them together somehow into one? First:
Predicate<object> viewFilter = f =>
{
ExternalUser u = f as ExternalUser;
return u.AgentName.ToLower().StartsWith(agentName.ToLower());
};
Second:
Predicate<object> viewFilter = f =>
{
ExternalUser u = f as ExternalUser;
return u.ExternalLogin.ToLower().StartsWith(login.ToLower());
};
And this is how joined predicate should look like.
Predicate<object> viewFilter = f =>
{
ExternalUser u = f as ExternalUser;
return u.ExternalLogin.ToLower().StartsWith(login.ToLower()) && u.AgentName.ToLower().StartsWith(agentName.ToLower());
};
I need this for WPF data grid filter where grid source is ICollectionView. So after I've created my predicate I set it into filter like this:
private void FilterByLogin(ICollectionView view, string login)
{
Predicate<object> viewFilter = f =>
{
ExternalUser u = f as ExternalUser;
return u.ExternalLogin.ToLower().StartsWith(login.ToLower());
};
view.Filter = viewFilter;
}
I would create two new methods:
public static Prediate<object> Cast<T>(Predicate<T> inner)
{
return new Predicate<object>(o => inner((T)o));
}
public static Predicate<T> And<T>(Predicate<T> p1, Predicate<T> p2)
{
return x => p1(x) && p2(x);
}
then you can remove the cast from your predicates and move it into the top-level:
Predicate<ExternalUser> first = u => u.AgentName.ToLower().StartsWith(agentName.ToLower());
Predicate<ExternalUser> second = u => u.ExternalLogin.ToLower().StartsWith(login.ToLower());
view.Filter = Cast(And(first, second));
It really should be as simple as this:
Predicate<object> viewFilter1 = f =>
{
ExternalUser u = f as ExternalUser;
return u.AgentName.ToLower().StartsWith(agentName.ToLower());
};
Predicate<object> viewFilter2 = f =>
{
ExternalUser u = f as ExternalUser;
return u.ExternalLogin.ToLower().StartsWith(login.ToLower());
};
Predicate<object> viewFilter = f => viewFilter1(f) && viewFilter2(f);
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