VB.NET How to check list against another list

Question

User941905567 posted

I am basically trying to check and see if an item is contained in a list . (See the .Contains() below) The list is a list of a class model in my project. What would I need to do to get this to work ? The error I get currently is "Value of type 'String' cannot be converted to 'AgentModAvailability' " ModId is a string value. Any suggestions would be greatly appreciated.  

--Jason

'Load the vms object 
Dim vms As List(Of Mods2Vm) = Mods2GetVms()

'Load agtspecificmods
  Dim bllagtspecificmods As Premium.BLL.AgentModAvailability = New Premium.BLL.AgentModAvailability()
  Dim agtspecificmods As New List(Of Premium.Model.AgentModAvailability)
  agtspecificmods = bllagtspecificmods.LoadArr().ToList()
 For Each v As Mods2Vm In vms
     If agtspecificmods.Contains(v.ModId) = True Then
        'Do Stuff
     END IF
   

 Next

Answer 1

User281315223 posted

You could evaluate all of the items within your collection to see if any meet your specific criteria (e.g. they have that specific ID) via LINQ:

agtspecificmods.Any(Function(v) v.SomeProperty = v.ModId) = True

Answer 2

User-719153870 posted

Hi Jazzcatone,

In addition to @Rion's reply, you can also use the Exists() method to check if a model with specific property value exists in the list.

Sub Main()
        Dim agtspecificmods As List(Of AgentModAvailability) = New List(Of AgentModAvailability)()
        Dim agent1 As AgentModAvailability = New AgentModAvailability() With {
            .property1 = "a"
        }
        Dim agent2 As AgentModAvailability = New AgentModAvailability() With {
            .property1 = "b"
        }
        Dim agent3 As AgentModAvailability = New AgentModAvailability() With {
            .property1 = "c"
        }
        agtspecificmods.Add(agent1)
        agtspecificmods.Add(agent2)
        agtspecificmods.Add(agent3)
        Dim vms As List(Of Mods2Vm) = New List(Of Mods2Vm)()
        Dim mods21 As Mods2Vm = New Mods2Vm() With {
            .ModId = "aa"
        }
        Dim mods22 As Mods2Vm = New Mods2Vm() With {
            .ModId = "b"
        }
        Dim mods23 As Mods2Vm = New Mods2Vm() With {
            .ModId = "cc"
        }
        vms.Add(mods21)
        vms.Add(mods22)
        vms.Add(mods23)

        For Each v As Mods2Vm In vms

            If agtspecificmods.Exists(Function(x) x.property1 = v.ModId) Then
                Console.WriteLine("1")
            Else
                Console.WriteLine("0")
            End If
        Next
    End Sub

    Public Class Mods2Vm
        Public Property ModId As String
    End Class

    Public Class AgentModAvailability

        Public Property property1 As String

    End Class

Output:

For more information, please check the doc List<T>.Contains(T) Method.

Why not use the Contains method, it's right there in the doc example?

I've tested it too and it works perfecetly in c# but not in vb.

To make Contains() feasible, it requires the class to inherit from itself:

public class Part : IEquatable<Part>
{
    public string PartName { get; set; }
    public int PartId { get; set; }

    public override string ToString()
    {
        return "ID: " + PartId + "   Name: " + PartName;
    }
    public override bool Equals(object obj)
    {
        if (obj == null) return false;
        Part objAsPart = obj as Part;
        if (objAsPart == null) return false;
        else return Equals(objAsPart);
    }
    public override int GetHashCode()
    {
        return PartId;
    }
    public bool Equals(Part other)
    {
        if (other == null) return false;
        return (this.PartId.Equals(other.PartId));
    }
    // Should also override == and != operators.
}

This can work in c#, but in vb it throws error:

I'm not export, but it seems that "Classes can inherit only from other classes" in vb.

Best Regard,

Yang Shen