Combining two expressions

Question

I have an Expression<func<Portfolio, bool>> and I want to add an extra condition if an expression is true, here is my code,

Expression<Func<Portfolio, bool>> condition = x =>
        x.Client == Params.Client
        && x.AnalysisDate == Params.AnalysisDate
        && x.AsOf <= Params.ReportDate

    if (Params.Names.Any())
    {
        //Here I want to add an extra condition to add the following to the condition
       && portfoliosParams.Names.Contains(x.Name);
    }

Any ideas?

https://stackoverflow.com/questions/22039753/how-to-add-another-condition-to-an-expression — Roman Ryzhiy, Dec 01 '22 at 10:56
since we know little about the types of your variables, please post an attempt how you want to apply the condition. Maybe it becomes clearer for you also — Mong Zhu, Dec 01 '22 at 11:00
Is there a relation between `Params` and `portfoliosParams` ? — Orace, Dec 01 '22 at 11:13
Does this answer your question? [How to create an Expression AND clause from two expressions](https://stackoverflow.com/questions/12684010/how-to-create-an-expression-and-clause-from-two-expressions) — Orace, Dec 01 '22 at 11:15
actually it would help us really to know the types of `portfoliosParams` and `Params` and the declaration of the `Portfolio` class — Mong Zhu, Dec 01 '22 at 11:21

score 1 · Answer 1 · answered Dec 01 '22 at 11:20

If Params.Names.Any() (shouldn't it be portfoliosParams.Names.Any() ?) is evaluated before you build the expression, the easiest way to achieve this is probably like so :

Expression<Func<Portfolio, bool>> condition;

if (Params.Names.Any())
{
    condition = x => x.Client == Params.Client &&
                     x.AnalysisDate == Params.AnalysisDate &&
                     x.AsOf <= Params.ReportDate &&
                     portfoliosParams.Names.Contains(x.Name);
}
else
{
    condition = x => x.Client == Params.Client &&
                     x.AnalysisDate == Params.AnalysisDate &&
                     x.AsOf <= Params.ReportDate;
}

Otherwise you should include the condition in the expression:

Expression<Func<Portfolio, bool>> condition = x =>
    x.Client == Params.Client &&
    x.AnalysisDate == Params.AnalysisDate &&
    x.AsOf <= Params.ReportDate &&
    (Params.Names.Count() == 0 || portfoliosParams.Names.Contains(x.Name));

Finally is you really need to build up the expression, there is already answers about expression combination.

Combining two expressions

1 Answers1