FirstOrDefault Condition : FirstOrDefault « LINQ « VB.Net

1. VB.Net
2. LINQ
3. FirstOrDefault

FirstOrDefault Condition

  


Imports System.IO
Imports System.Reflection
Imports System.Linq
Imports System.Xml.Linq
Imports System.Collections
Imports System.Collections.Generic


Public Class Project
    Public ProjectID As Integer
    Public ProjectName As String
    Public Category As String
    Public Cost As Decimal
    Public YearLength As Integer
End Class

Public Class Employee
    Public EmployeeID As String
    Public CompanyName As String
    Public Address As String
    Public City As String
    Public Region As String
    Public PostalCode As String
    Public Country As String
    Public Phone As String
    Public Fax As String
    Public Payments As Payment()
End Class

Public Class Payment
    Public PaymentID As Integer
    Public PaymentDate As DateTime
    Public Total As Decimal
End Class



Public Class MainClass
    Public Shared Sub Main()
        Dim projectList As List(Of Project) = New List(Of Project)
        projectList.Add(New Project With {.ProjectID = 1, .ProjectName = "A", .Category = "Design", .Cost = 18D, .YearLength = 39})
        projectList.Add(New Project With {.ProjectID = 2, .ProjectName = "B", .Category = "Testing", .Cost = 19D, .YearLength = 17})
        projectList.Add(New Project With {.ProjectID = 3, .ProjectName = "C", .Category = "Coding", .Cost = 10D, .YearLength = 13})
        projectList.Add(New Project With {.ProjectID = 4, .ProjectName = "D", .Category = "Meeting", .Cost = 22D, .YearLength = 53})
        projectList.Add(New Project With {.ProjectID = 5, .ProjectName = "E", .Category = "Writing", .Cost = 21.35D, .YearLength = 0})
        projectList.Add(New Project With {.ProjectID = 6, .ProjectName = "F", .Category = "Testing", .Cost = 25D, .YearLength = 120})
        projectList.Add(New Project With {.ProjectID = 7, .ProjectName = "G", .Category = "Coding", .Cost = 30D, .YearLength = 15})
        projectList.Add(New Project With {.ProjectID = 8, .ProjectName = "H", .Category = "Design", .Cost = 40D, .YearLength = 6})
        projectList.Add(New Project With {.ProjectID = 9, .ProjectName = "I", .Category = "Coding", .Cost = 97D, .YearLength = 29})


        Dim employeeList As List(Of Employee) = New List(Of Employee)

        employeeList.Add(New Employee With {.EmployeeID = 1, .CompanyName = "Company A", .Address = "Street 1", .City = "City 1", .Region = "North"})
        employeeList.Add(New Employee With {.EmployeeID = 2, .CompanyName = "Company B", .Address = "Street 2", .City = "City 2", .Region = "South"})
        employeeList.Add(New Employee With {.EmployeeID = 3, .CompanyName = "Company C", .Address = "Street 3", .City = "City 3", .Region = "West"})
        employeeList.Add(New Employee With {.EmployeeID = 4, .CompanyName = "Company D", .Address = "Street 4", .City = "City 4", .Region = "East"})
        employeeList.Add(New Employee With {.EmployeeID = 5, .CompanyName = "Company E", .Address = "Street 5", .City = "City 5", .Region = "North"})
        employeeList.Add(New Employee With {.EmployeeID = 6, .CompanyName = "Company F", .Address = "Street 6", .City = "City 6", .Region = "South"})




        Dim project789 = Aggregate prod In projectList _
                         Into FirstOrDefault(prod.ProjectID = 789)

        Console.WriteLine("Project 789 exists: " & (project789 IsNot Nothing))
    End Sub


End Class

   
    
  

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