Create GroupBy Statments Dynamically By Strings Array - Linq to Entity

Question

I've got an action which loads an array of strings which were checked by thier appropriate checkboxes on the page:

        public ActionResult Test1(string[] checked_strings)

I would like to use this strings which are equal on their name to the entities which i want to create a groupby statement dynamically.

Which will go on something like this:

            bool bChecked = Request.Form["checked_strings"].Contains("true");
            cmpqry =   from x in checked_strings
                       from y in typeof(Company).GetProperties()
                       where y.Name == x.ToString()
     // Create the groupby statement for the properties matched with the strings //

Any idea how to pull this over?

cmpqry holds the IEnumarable list(later returned to view) of the model's class.

Dynamic linq may be your answer, stackoverflow.com/questions/2448611/… — Slicksim
– Slicksim, Commented Feb 26, 2013 at 9:48
Already tried that and I can't convert it back to the EF model and list it properly to the view. If you think it's possible i'd like an example.. Thanks. — JBntis
– JBntis, Commented Feb 26, 2013 at 10:07
Couldn't manage to use the "GroupBy" of dynamic linq, it throws exeption as from this example : var groups = Model.GroupBy("SomeColumn, SomeOtherColumn") even after i've added the library file DynamicLibrary.cs - Please help!! — JBntis
– JBntis, Commented Feb 26, 2013 at 14:28

Evgeny · Accepted Answer · 2013-03-03 22:21:09Z

2

Here's the code sample that works - you should be able to supply the fields you want to group on in the order you want them to be grouped:

public class Company
{
    public int CompanyID { get; set; }
    public string CompanyName { get; set; }
    public string SubBranchName { get; set; }
    public string ProductName { get; set; }
}

public static class MyEnumerableExtensions
{
    /// <summary>
    /// Applies grouping to the collection of elements using the selectors specified
    /// </summary>
    /// <typeparam name="TElement">Type of the element</typeparam>
    /// <param name="elements">Elements to be grouped</param>
    /// <param name="groupSelectors">Selectors, or properties to be grouped on</param>
    /// <returns></returns>
    public static IEnumerable<GroupResult> GroupByMany<TElement>(
        this IEnumerable<TElement> elements,
        params Func<TElement, object>[] groupSelectors)
    {
        if (groupSelectors.Length > 0)
        {
            var selector = groupSelectors.First();

            //reduce the list recursively until zero
            var nextSelectors = groupSelectors.Skip(1).ToArray();
            return
                elements.GroupBy(selector).Select(
                    g => new GroupResult
                    {
                        Key = g.Key,
                        Items = g,
                        SubGroups = g.GroupByMany(nextSelectors)
                    });
        }
        return null;
    }

    public class GroupResult
    {
        public object Key { get; set; }
        public IEnumerable Items { get; set; }
        public IEnumerable<GroupResult> SubGroups { get; set; }
    }
}



//Your usage of the GroupByMany
IEnumerable<Company> list = new List<Company>
 {new Company{CompanyID = 1, CompanyName = "Company1", ProductName = "Product1", SubBranchName = "SB1"},
 new Company{CompanyID = 2, CompanyName = "Company1", ProductName = "Product2", SubBranchName = "SB2"},
 new Company{CompanyID = 3, CompanyName = "Company1", ProductName = "Product3", SubBranchName = "SB1"},
 new Company{CompanyID = 4, CompanyName = "Company2", ProductName = "Product4", SubBranchName = "SB2"},
 new Company{CompanyID = 5, CompanyName = "Company2", ProductName = "Product1", SubBranchName = "SB2"},
 new Company{CompanyID = 6, CompanyName = "Company2", ProductName = "Product2", SubBranchName = "SB1"},
 new Company{CompanyID = 7, CompanyName = "Company2", ProductName = "Product3", SubBranchName = "SB2"},
 new Company{CompanyID = 8, CompanyName = "Company3", ProductName = "Product4", SubBranchName = "SB2"},
 new Company{CompanyID = 9, CompanyName = "Company3", ProductName = "Product3", SubBranchName = "SB1"},
 new Company{CompanyID = 10, CompanyName = "Company3", ProductName = "Product2", SubBranchName = "SB2"},
 };

    var groupedByProductNameThenSubBranchName = list.GroupByMany(p => p.ProductName, p => p.SubBranchName);

    foreach (var groupResult in groupedByProductNameThenSubBranchName)
    {
        foreach (var result in groupResult.SubGroups)
        {
            foreach (var groupResult1 in result.Items)
            {
                Company company = groupResult1 as Company;
                Debug.Print(String.Format("ProductName: {0}, SubBranchName: {1}", company.ProductName, company.SubBranchName));
            }
        }
    }

    var groupedBySubBranchNameThenCompany = list.GroupByMany(p => p.SubBranchName, p => p.CompanyName);

    foreach (var groupResult in groupedBySubBranchNameThenCompany)
    {
        foreach (var result in groupResult.SubGroups)
        {
            foreach (var groupResult1 in result.Items)
            {
                Company company = groupResult1 as Company;
                Debug.Print(String.Format("SubBranchName: {0}, CompanyName: {1}", company.SubBranchName, company.CompanyName));
            }
        }
    }

The first "foreach" prints out

ProductName: Product1, SubBranchName: SB1
ProductName: Product1, SubBranchName: SB2
ProductName: Product2, SubBranchName: SB2
ProductName: Product2, SubBranchName: SB2
ProductName: Product2, SubBranchName: SB1
ProductName: Product3, SubBranchName: SB1
ProductName: Product3, SubBranchName: SB1
ProductName: Product3, SubBranchName: SB2
ProductName: Product4, SubBranchName: SB2
ProductName: Product4, SubBranchName: SB2

The second "foreach" prints out

SubBranchName: SB1, CompanyName: Company1
SubBranchName: SB1, CompanyName: Company1
SubBranchName: SB1, CompanyName: Company2
SubBranchName: SB1, CompanyName: Company3
SubBranchName: SB2, CompanyName: Company1
SubBranchName: SB2, CompanyName: Company2
SubBranchName: SB2, CompanyName: Company2
SubBranchName: SB2, CompanyName: Company2
SubBranchName: SB2, CompanyName: Company3
SubBranchName: SB2, CompanyName: Company3

Hope this helps!

answered Mar 3, 2013 at 22:21

Evgeny

3,3527 gold badges42 silver badges51 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Umar F Khawaja Over a year ago

Maybe use IQueryable<TElement> and Expression<Func<TElement, object>> to be able to group "natively" and hook into the expression tree built and sent back to the DB?

JBntis Over a year ago

And if I want to groupBy only one group without subgroups?

JBntis Over a year ago

Well it's awesome evgeny, How do you pass the GroupByMany(p => p.DynamicField1, p => p.DynamicField2 ... p => p.DynamicFieldN);and do all the subgroup mining later dynamically? with for loop from strings or what? , The primary cause is to make generate a Company after the groupby and pass it to the view. thanks alot!

JBntis Over a year ago

Another important thing, When you use: --- Company company = groupResult1 as Company; --- The whole company is filled and not only the fields which i wanted to groupby with, How can the company entity only have only the proper fields and leave the other null, etc? , Or should i just cluase the visibility for those fields in the view(The load time is better if only the needed grouped fields will be loaded!)

JBntis Over a year ago

Also the company should be filled and not overided on the first raw every time.

|

Evgeny · Accepted Answer · 2013-03-03 10:28:50Z

1

I can't say exactly how relevant this is to your particular problem, but if you have a field you want to group your data on you can write a query similar to the following, which groups the blog posts on the year they were created in

var results = from allPosts in db.Posts.OrderBy(p => p.DateCreated)
              group allPosts by allPosts.DateCreated.Year into postsByYear;

The "results" here is the enumeration of groups - in this case, posts published in a certain year.

This can be further extended to create child groups within the "first level" - posts by the month groups similar to

var results = from allPosts in db.Posts.OrderBy(p => p.DateCreated)
              group allPosts by allPosts.DateCreated.Year into postsByYear

              select new
              {
                  postsByYear.Key,
                  SubGroups = from yearLevelPosts in postsByYear
                              group yearLevelPosts by yearLevelPosts.DateCreated.Month into postsByMonth;
              };

Now the SubGroups is the enumeration of posts within the month. There is more information here (may be very helpful)

http://blogs.msdn.com/b/mitsu/archive/2007/12/22/playing-with-linq-grouping-groupbymany.aspx

and here (my application of the previous link to a particular problem I had)

http://www.ynegve.info/Post/156/implementing-a-tree-view-small-case-study

If that looks like what you need, but you still can't make it work, please post more info about your model.

answered Mar 3, 2013 at 10:28

Evgeny

3,3527 gold badges42 silver badges51 bronze badges

1 Comment

JBntis Over a year ago

Hey Evgeny, Thank you for your time. I've made a more well explained post here: forums.asp.net/t/1885915.aspx/… Basicly, I have several fields that i want to pass as variable to the groupBy clause instead of hard-coded grouping by casing every possible scenerio. To be able to do something like : IEnumerable<Company> afs = cmpqry.GroupBy("CompanyName", "SubBranchName", "ProductName"); and afterward when users checks different fields ill be able to pass other values: IEnumerable<Company> afs = cmpqry.GroupBy("CompanyName", "SomeName");

Collectives™ on Stack Overflow

Create GroupBy Statments Dynamically By Strings Array - Linq to Entity

2 Answers 2

6 Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

6 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related