how to append one class to another of same in vb.net - vb.net

Question

PropertyPolicy is a class that defines a collection of several fields/entities. Sometimes two separate functions are needed to build out the collection. (LoadEstateAIN and LoadAIN). I need to combine the results of both classes but have tried concat but get a cast exception. What would work here?
Public Class PropertyPolicy
Private agentfield As Entity
Private aininsuredfield() As Entity
Private billinginfofield As BillingInfo
Private cancellationdatefield As Date
Private claimsfield() As Claims
Public Property Agent As Entity
Get
Return Me.agentfield
End Get
Set(ByVal value As Entity)
Me.agentfield = value
End Set
End Property
Public Property AINInsured() As Entity()
Get
Return Me.aininsuredfield
End Get
Set(ByVal value As Entity())
Me.aininsuredfield = value
End Set
End Property
Public Property BillingInfo As BillingInfo
Get
Return Me.billinginfofield
End Get
Set(ByVal value As BillingInfo)
Me.billinginfofield = value
End Set
End Property
Public Property CancellationDate As Date
Get
Return Me.cancellationdatefield
End Get
Set(ByVal value As Date)
Me.cancellationdatefield = value
End Set
End Property
Public Property Claims() As Claims()
Get
Return Me.claimsfield
End Get
Set(ByVal value As Claims())
Me.claimsfield = value
End Set
End Property
End Class
Dim propTemp1 As New PropertyPolicy
Dim propTemp2 As New PropertyPolicy
Dim propTempComb As New PropertyPolicy
propTemp1.AINInsured = LoadEstateAIN(policyid, asofDate, lob, NINclientid, estatecompany)
propTemp2.AINInsured = LoadAIN(policyid, asofDate, lob, NINclientid, estatecompany)
propTempComb.AINInsured = propTemp1.AINInsured.Concat(propTemp2.AINInsured)

Answer 1

The result of Concat is not an array; it is an IEnumerable(Of T). In your case it is an IEnumerable(Of Entity). You just need to add ToArray() to the end of the Concat if you want to assign it back to an array.
propTempComb.AINInsured = propTemp1.AINInsured.Concat(propTemp2.AINInsured).ToArray()
Breaking down this line of code:
[instance3].[property] = [instance1].[property].Concat([instance2].[property])
Assigns the result of the Concat to the property, but the property is an array so you need to change the result of Concat which is an IEnumerable(Of Entity) into an array which is trivial with ToArray.
I could go further and recommend that you don't use arrays as public members, rather IEnumerable. Also, auto-properties would be a better choice for some of these Public/Public properties.
Public Class PropertyPolicy
Private aininsuredfield As Entity()
Private claimsfield As Claims()
Public Property Agent As Entity
Public Property BillingInfo As BillingInfo
Public Property CancellationDate As Date
Public Property AINInsured() As IEnumerable(Of Entity)
Get
Return aininsuredfield
End Get
Set(value As IEnumerable(Of Entity))
aininsuredfield = value.ToArray()
End Set
End Property
Public Property Claims() As IEnumerable(Of Claims)
Get
Return claimsfield
End Get
Set(value As IEnumerable(Of Claims))
claimsfield = value.ToArray()
End Set
End Property
End Class
And btw, that would cause your original code to work without ToArray()
propTempComb.AINInsured = propTemp1.AINInsured.Concat(propTemp2.AINInsured)