How to create dynamic query with for loop?

Question

I want to create query dynamically based on entered number and make it to array to get data from view, so I can create condition to filter it, but my query only works for 3 entered numbers.

var query = from bs in dc.VwResourceAssignments select bs;

var listReqNumber = new[] {123, 456, 789};

My current query is:

if (listReqNumber.Length == 1)
{
    query = query.Where(p => p.RequisitionNumber.Contains(listReqNumber[0]));
}
else if (listReqNumber.Length == 2)
{
    query = query.Where(p => p.RequisitionNumber.Contains(listReqNumber[0]) ||
                             p.RequisitionNumber.Contains(listReqNumber[1]));
}
else if (listReqNumber.Length == 3)
{
    query = query.Where(p => p.RequisitionNumber.Contains(listReqNumber[0]) ||
                             p.RequisitionNumber.Contains(listReqNumber[1]) ||
                             p.RequisitionNumber.Contains(listReqNumber[2]));
}

Is there any way to make it dynamically so I can input requisition number as many as I want?

i would recommend searching for a predicatebuilder class - this is a solved problem so you should be in luck — jazb
– jazb, Commented Dec 10, 2018 at 3:15
you should not be using vs2010. we are now reaching the end of 2018 with vs 2019 already in preview. strongly recommend you upgrade — jazb
– jazb, Commented Dec 10, 2018 at 3:18

Dmitrii Bychenko · Accepted Answer · 2018-12-10 08:50:13Z

1

Let's generalize the problem: if we have an arbitrary listReqNumber array we want to implement

query = query.Where(
   p => p.RequisitionNumber.Contains(listReqNumber[0]) ||
        p.RequisitionNumber.Contains(listReqNumber[1]) || 
        ...
        p.RequisitionNumber.Contains(listReqNumber[listReqNumber.Length - 1])
);

or - let's get rid of || - we want any item req withing listReqNumber be contained in p.RequisitionNumber

 // doesn't compile - just the idea   
 query = query.Where(p => p.RequisitionNumber.Contains(any req in listReqNumber));

Pity, we can't put any req in listReqNumber but we can swap listReqNumber and p.RequisitionNumber and finally have a valid query:

 query = query.Where(p => listReqNumber.Any(req => p.RequisitionNumber.Contains(req)));

edited Dec 10, 2018 at 8:50

answered Dec 10, 2018 at 8:35

Dmitrii Bychenko

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Comments

Vijunav Vastivch · Accepted Answer · 2018-12-10 03:51:54Z

0

How about if you use directly like this:

var result = from p in query where listReqNumber.Contains(p.RequisitionNumber) select p;

answered Dec 10, 2018 at 3:51

Vijunav Vastivch

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2 Comments

gilliduck Over a year ago

Or to use the syntax you're already using var result = query.Where(p => listReqNumber.Contains(p.RequisitionNumber);

Giri22 Over a year ago

i have tried it before, but its work if RequisitionNumber exactly same, for example, data in database is 45321 , the number that i enter is 453, then the result is nothing, I have to enter exactly 45321, any idea for my chase?

Petr Bogoyavlenskiy · Accepted Answer · 2018-12-10 04:27:08Z

0

var data = query.Where(q =>
  q.RequisitionNumber.Any(w => listReqNumber.Contains(w))
);

answered Dec 10, 2018 at 4:27

Petr Bogoyavlenskiy

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Comments

Gauravsa · Accepted Answer · 2018-12-10 06:33:52Z

0

You can use dynamic linq. Link is here: https://weblogs.asp.net/scottgu/dynamic-linq-part-1-using-the-linq-dynamic-query-library

then have a function like below:

string GetQuery(int num)
{
    return $"p.RequisitionNumber.Contains(listReqNumber[{num}])";
}

Create a query like below in Main:

string testQuery = string.Empty; // or use StringBuilder then convert to string.
int length = 4;
for (int temp = 1; temp <= length; temp ++)
     testQuery += testQuery.Length == 0 ? GetQuery(temp - 1) : " || " + GetQuery(temp);

then use dynamic linq like:

var query = northwind.Products
                         .Where(testQuery).OrderBy("SupplierID");

edited Dec 10, 2018 at 6:33

answered Dec 10, 2018 at 6:25

Gauravsa

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