PredicateBuilder Usage - C# Discussion Boards

11-Jul-18 6:29

I have a MEF plugin that runs test for a medical instrument. The instrument starts the test service, and that service loads the MEF plugin and calls it's Execute method. This all runs in another thread.

The MEF plugin gets its settings from a Config file. Changes are made to the Config file using an editor designed for it. This editor is a stand alone EXE not connected to the instrument in any way.

The configuration can be set to run the tests for [n] times. This gives techs time to look at the instrument while its running.

1) Instrument starts the test process.
2) Test process loads the MEF plugin.
3) MEF plugin reads config file.
4) Tests inside the plugin execute using settings from config file.
5) At end of test, start next iteration until [n] is reached. Goto step 4.

What I'm wondering is this... Is it possible for an external EXE to somehow get data from the MEF plugin in real time? And, it also could commands be sent into the plugin, such as stop, pause, etc?

Thanks

If it's not broken, fix it until it is.
Everything makes sense in someone's mind.
Ya can't fix stupid.

Pete O'Hanlon11-Jul-18 7:19

Pete O'Hanlon

11-Jul-18 7:19

You could easily use self-hosted WCF to do this. Set it up to publish messages via named pipes and it'll run no problem.

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Kevin Marois11-Jul-18 7:40

11-Jul-18 7:40

Thanks, I'll look into that

If it's not broken, fix it until it is.
Everything makes sense in someone's mind.
Ya can't fix stupid.

Nathan Minier12-Jul-18 1:10

Nathan Minier

12-Jul-18 1:10

I don't like the bloat of WCF, but you can do secure named pipes pretty trivially without it.

"Never attribute to malice that which can be explained by stupidity."
- Hanlon's Razor

Pete O'Hanlon12-Jul-18 1:40

Pete O'Hanlon

12-Jul-18 1:40

Self hosted WCF doesn't add much at all. It's incredibly trivial.

This space for rent

PredicateBuilder Usage

Kevin Marois10-Jul-18 17:45

10-Jul-18 17:45

I've never used PredicateBuilder before. If anyone has used it, I could use some help

List<PurchasingEntity> results = null;

IQueryable<PurchasingEntity> query = (from c in db.Companies
                                        join p in db.Projects on c.Id equals p.CompanyId
                                        join j in db.Jobs on p.Id equals j.ProjectId
                                        select new PurchasingEntity
                                        {
                                            CompanyId = c.Id,
                                            ProjectId = p.Id,
                                            JobId = j.Id,
                                            Phase = j.Phase,
                                            Quantity = j.Quantity.HasValue ? j.Quantity.Value : 0,
                                            StartDate = j.StartDate.HasValue ? j.StartDate : null
                                        });

var predicate = PredicateBuilder.True<Purchasing>();

if (companyId > 0)
{
    predicate = predicate.And(i => i.CompanyId == companyId);
}

if (projectId    > 0)
{
    predicate = predicate.And(i => i.ProjectId == projectId);
}

if (startDate != null)
{
    predicate = predicate.And(i => i.StartDate >= startDate);
}

if (endDate != null)
{
    predicate = predicate.And(i => i.StartDate <= endDate);
}

results = query.Where(predicate); // <===== ERROR HERE
return results.ToList();

The compilation error is

cannot convert from 'System.Linq.Expressions.Expression<System.Func<Jayhawk.DAL.DataContext.Purchasing, bool>>' to 'System.Linq.Expressions.Expression<System.Func<Jayhawk.Entities.PurchasingEntity, int, bool>>'

Not quitre sure what's wrong here? Can anyone help?

If it's not broken, fix it until it is.
Everything makes sense in someone's mind.
Ya can't fix stupid.

Gerry Schmitz10-Jul-18 20:51

Gerry Schmitz

10-Jul-18 20:51

List<PurchasingEntity> results = null;

<pre>IQueryable<PurchasingEntity> query =

var predicate = PredicateBuilder.True<Purchasing>();

results = query.Where(predicate); // <===== ERROR HERE

"(I) am amazed to see myself here rather than there ... now rather than then".
― Blaise Pascal

Kevin Marois11-Jul-18 5:15

11-Jul-18 5:15

I must have stared at that for an hour. Just didn't see it

var predicate = PredicateBuilder.True<PurchasingEntity>();
.
.
.
results = query.Where(predicate).ToList();

This works now

Thanks!

If it's not broken, fix it until it is.
Everything makes sense in someone's mind.
Ya can't fix stupid.

Mycroft Holmes10-Jul-18 22:48

Mycroft Holmes

10-Jul-18 22:48

Bugger that looked really useful but it is in c#7, VS 2017. We are stuck with 2015.

Never underestimate the power of human stupidity
RAH

Kevin Marois11-Jul-18 5:14

11-Jul-18 5:14

public static class PredicateBuilder
{
    public static Expression<Func<T, bool>> True<T>() { return f => true; }
    public static Expression<Func<T, bool>> False<T>() { return f => false; }

    public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1,
                                                        Expression<Func<T, bool>> expr2)
    {
        var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
        return Expression.Lambda<Func<T, bool>>
                (Expression.OrElse(expr1.Body, invokedExpr), expr1.Parameters);
    }

    public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1,
                                                            Expression<Func<T, bool>> expr2)
    {
        var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
        return Expression.Lambda<Func<T, bool>>
                (Expression.AndAlso(expr1.Body, invokedExpr), expr1.Parameters);
    }
}

If it's not broken, fix it until it is.
Everything makes sense in someone's mind.
Ya can't fix stupid.