How to remove duplicate records from a List<T> in C#

kaushik debnath

I want to remove the duplicates from the List, for that I am using following code:

public List ContainerLevelDetails { get; set; }

public class ContainerLevelDetailsResponse
{
public long ContainerId { get; set; }
public string Container { get; set; }
public string Pallet { get; set; }
public string SKU { get; set; }
public long CaseCount { get; set; }
}

List containerLevelDetails =
new List();

booking.ContainerLevelDetails = containerLevelDetails.Distinct().ToList();

But its not working and did not giving unique records. Its not able to remove the duplicates.

Please suggest in this.

3 Replies

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Sachin Singh5y ago
Another approach is to use groupBy,
booking.ContainerLevelDetails = containerLevelDetails.GroupBy(x => x.ContainerId ).Select(y => y.First());
kaushik debnath5y ago
Any of the three solutions did not worked for me.

public List ContainerLevelDetails { get; set; }

public class ContainerLevelDetailsResponse
{
public long ContainerId { get; set; }
public string Container { get; set; }
public string Pallet { get; set; }
public string SKU { get; set; }
public long CaseCount { get; set; }
}

public class DistinctItemComparer : IEqualityComparer
{
public bool Equals(ContainerLevelDetailsResponse x, ContainerLevelDetailsResponse y)
{
return x.ContainerId == y.ContainerId &&
x.Container == y.Container &&
x.Pallet == y.Pallet &&
x.SKU == y.SKU &&
x.CaseCount == y.CaseCount;
}
public int GetHashCode(ContainerLevelDetailsResponse obj)
{
return obj.ContainerId.GetHashCode() ^
obj.Container.GetHashCode() ^
obj.Pallet.GetHashCode() ^
obj.SKU.GetHashCode() ^
obj.CaseCount.GetHashCode();
}
}

var dtShipmentDetails = dtTrace.Tables[4];
if(dtShipmentDetails.Rows.Count > 0)
{
traceDetails.Shipments = new List();
List containerLevelDetails = new List();
foreach (DataRow rd in dtShipmentDetails.Rows)
{
var bookingRes = JsonConvert.DeserializeObject>((string)rd["BookingData"]);
var booking = bookingRes[0];
booking.BookingId = (long)rd["BookingId"];
booking.BookingTypeId = (long)rd["BookingTypeId"];
booking.BookingType = (string)rd["BookingType"];
booking.ContainerCount = (int)rd["ContainerCount"];
#region User Story 4107 - Implementation
containerLevelDetails = JsonConvert.DeserializeObject> ((string)rd["ContainerLevelDetails"]);
booking.ContainerLevelDetails = containerLevelDetails.Distinct(new DistinctItemComparer()).ToList();

traceDetails.Shipments.Add(booking);
}

public class DistinctItemComparer : IEqualityComparer
{
public bool Equals(ContainerLevelDetailsResponse x, ContainerLevelDetailsResponse y)
{
return x.ContainerId == y.ContainerId &&
x.Container == y.Container &&
x.Pallet == y.Pallet &&
x.SKU == y.SKU &&
x.CaseCount == y.CaseCount;
}
public int GetHashCode(ContainerLevelDetailsResponse obj)
{
return obj.ContainerId.GetHashCode() ^
obj.Container.GetHashCode() ^
obj.Pallet.GetHashCode() ^
obj.SKU.GetHashCode() ^
obj.CaseCount.GetHashCode();
}
}

Duplicates records still coming
Sachin Singh5y ago
Distinct doesn't work for complex types, there are 3 techniques to overcome this.
Method 1. Override Equals and GetHasCode
public class ContainerLevelDetailsResponse
{
public long ContainerId { get; set; }
public string Container { get; set; }
public string Pallet { get; set; }
public string SKU { get; set; }
public long CaseCount { get; set; }

public override bool Equals(object obj)
{
return this.ID == ((ContainerLevelDetailsResponse)obj).ContainerId && this.Container == ((ContainerLevelDetailsResponse)obj).Container ;
}
public override int GetHashCode()
{
return this.ContainerId.GetHashCode() ^ this.Container .GetHashCode();
}

}

now it will work
booking.ContainerLevelDetails = containerLevelDetails.Distinct().ToList();
Method 2. Don't override the Equals or HasCode, but create an EqualityComparer and use second overloaded version of Distinct().
public class MyComparer : IEqualityComparer
{
    public bool Equals(ContainerLevelDetailsResponse x, ContainerLevelDetailsResponse y)
    {
        return x.ContainerId == y.ID && x.Container== y.Name;
    }

    public int GetHashCode(ContainerLevelDetailsResponseobj)
    {
        return obj.ContainerId .GetHashCode() ^ obj.Container.GetHashCode();
    }
}
now it will work
booking.ContainerLevelDetails = containerLevelDetails.Distinct(new MyCompare()).ToList();
Method 3 (My Favorite):- Project items to an anonymous type that will automatically override the Equals() method for you.
booking.ContainerLevelDetails = containerLevelDetails.select(x=>new {x.ContainerId,x.Container,x.Pallet,x.SKU,x.CaseCount}).Distinct().ToList();