How to create chained/deferred query for Find*

[khcha...@gmail.com]

Hi Guys,

I am struggling to figure out a way to construct query for Find.

basically i would like to have something like

var myquery; //.......... for init query
if (xxxxx)
{
myquery = xxxxx AND YYYYY
}
else
{
myquery = XXXXX
}

mySharpRepo.FindAll(query);

any idea?
in particular, i don't know what data Type should i use for the myquery

[Jeff Treuting]

The Type of the query depends on the type of the repository. So if you have

IRepository<User> mySharpRepo

Then the conditional for building your query could look like this:

Expression<Func<User, bool>> query = null;

if (true)
{
query = x => x.IsBasicUser;
}
else
{
query = x => x. IsBasicUser && x.UserTypeId == 1;
}

mySharpRepo.FindAll(query);

There are other ways to do it as well but that would work.

Jeff

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[khcha...@gmail.com]

I see. didn't know you can create lambda expression like that.

how about if i want to chain query together base on condition?

for example:

Expression<Func<User, bool>> query = null;

if (filterByType == true)
{
query = z => z.Type == APPLE
}

if (filterByCountry == True)
{
AND query = z => z.Country == AUSTRALIA
}

So that if filterByCountry and filterByType are both true, the query should become something like
z => z.Type == APPLE && z.Country == AUSTRALIA

and if only filterByCountry is set, then the query should be
z => z.Country == AUSTRALIA

Any thought?

[Jeff Treuting]

You can do it with expressions simply like:

Expression<Func<User,bool>> query = x => x.IsActive;

If(filterByType)
{
query = query.AndAlso(x => x.Type == "APPLE");
}

So you can just compose new expressions by combining them with other expressions using And, Or, Not, etc.

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[Nelson Chan]

Thank you Jeff, you totally saved my day.

i spent the whole morning looking into SharpRepository.Specification and hitting walls.

Regards,
Nelson Chan

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