distinct values in linq

Question

User639567535 posted

i try linq query

<asp:DropDownList ID="regiondrop" runat="server" AutoPostBack="True" 
onselectedindexchanged="regiondrop_SelectedIndexChanged">
</asp:DropDownList> 

<br /><br />

i try to show distinct values in drop-down 

on page load 

i try this query to get values

T1 tea = new T1();
                var list1 = tea.t1.ToList();
                var list = (from ta in list1
                            
                            orderby ta.Region
                            select new { ta.Region,ta.RegionID }).Distinct().ToList();

but this shows all same values where as i want distinct values

any solution?

Answer 1

User-821857111 posted

You need to use the debugger to see what value is being passed to the Convert.ToInt32 method. It may not be what you expect.

Answer 2

User639567535 posted

You need to use the debugger to see what value is being passed to the Convert.ToInt32 method. It may not be what you expect.

please check update question

Answer 3

User-821857111 posted

Please don't use the Edit button to completely change your question. If your original question is resolved, mark the thread as answered then start a new thread for the new question.

Answer 4

User639567535 posted

the question i edit is not resolved but now i post a new quest

Answer 5

User36583972 posted

Hi Bakhtawar,

You can try the following two methods.

1: Define a TestTTComparare  class.

TestTTComparare Class:

 class TestTTComparare : IEqualityComparer<TestTT>
    {
        public bool Equals(TestTT x, TestTT y)

        {
            if (Object.ReferenceEquals(x, y)) return true;

            if (Object.ReferenceEquals(x, null) ||

                Object.ReferenceEquals(y, null))

                return false;

            return x.Region == y.Region && x.RegionID == y.RegionID;
        }

        public int GetHashCode(TestTT number)
        {
            if (Object.ReferenceEquals(number, null)) return 0;

            int hashTextual = number.Region == null
                ? 0 : number.Region.GetHashCode();

            int hashDigital = number.RegionID.GetHashCode();
            return hashTextual ^ hashDigital;
        }
    }

 var list2 = tt1.ToList().Distinct(new TestTTComparare());

2: Define a DistinctBy method.

public static class LinqExtendsDis
    {
        public static IEnumerable<TSource> DistinctBy<TSource, TKey>
    (this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
        {
            HashSet<TKey> seenKeys = new HashSet<TKey>();
            foreach (TSource element in source)
            {
                if (seenKeys.Add(keySelector(element)))
                {
                    yield return element;
                }
            }
        }
    }

 var list3 = tt1.DistinctBy(p => new { p.Region, p.RegionID });

Best Regards,

Yohann Lu

Answer 6

User639567535 posted

hi install morelinq and add reference file

then i try this 

protected void Page_Load(object sender, EventArgs e)
            {


                T1 tea = new T1();
                var list1 = tea.table1.ToList();

                var list = (from ta in list1
                            select new
                            {
                                RID = ta.RegionID,
                                Region = ta.Region
                            }).ToList();
                var list3 = list.DistinctBy(p => new { p.Region, p.RegionID });
                 
            
                if(!Page.IsPostBack)
                {
                    regiondrop.DataSource = list;           
                    regiondrop.DataTextField = "Region";
                    regiondrop.DataValueField = "RegionID";
                    regiondrop.DataBind();
                 
                  }
               
            }

but there is error in distinctby

Answer 7

User36583972 posted

Hi Bakhtawar,

Change your code as the below.

var list = (from ta in tt1
                        select new
                        {
                            RID = ta.RegionID,
                            Region = ta.Region
                        }).ToList();
            var list3 = list.DistinctBy(p => new { p.Region, p.RID });

    if (!Page.IsPostBack)
            {
                regiondrop.DataSource = list;
                regiondrop.DataTextField = "Region";
                regiondrop.DataValueField = "RID";
                regiondrop.DataBind();

            }

Best Regards,

Yohann Lu