Tomar cláusula (Visual Basic)
Returns a specified number of contiguous elements from the start of a collection.
Take count
Parts
- count
Required. A value or an expression that evaluates to the number of elements of the sequence to return.
Comentários
The Take clause causes a query to include a specified number of contiguous elements from the start of a results list. The number of elements to include is specified by the count parameter.
You can use the Take clause with the Skip clause to return a range of data from any segment of a query. To do this, pass the index of the first element of the range to the Skip clause and the size of the range to the Take clause. In this case, the Take clause must be specified after the Skip clause.
When you use the Take clause in a query, you may also need to ensure that the results are returned in an order that will enable the Take clause to include the intended results. For more information about ordering query results, see Cláusula Order By (Visual Basic).
You can use the TakeWhile clause to specify that only certain elements be returned, depending on a supplied condition.
Exemplo
The following code example uses the Take clause together with the Skip clause to return data from a query in pages. The GetCustomers function uses the Skip clause to bypass the customers in the list until the supplied starting index value, and uses the Take clause to return a page of customers starting from that index value.
Public Sub PagingSample()
Dim pageNumber As Integer = 0
Dim pageSize As Integer = 10
Dim customersPage = GetCustomers(pageNumber * pageSize, pageSize)
Do While customersPage IsNot Nothing
Console.WriteLine(vbCrLf & "Page: " & pageNumber + 1 & vbCrLf)
For Each cust In customersPage
Console.WriteLine(cust.CustomerID & ", " & cust.CompanyName)
Next
Console.WriteLine(vbCrLf)
pageNumber += 1
customersPage = GetCustomers(pageNumber * pageSize, pageSize)
Loop
End Sub
Public Function GetCustomers(ByVal startIndex As Integer,
ByVal pageSize As Integer) As List(Of Customer)
Dim customers = GetCustomerList()
Dim returnCustomers = From cust In customers
Skip startIndex Take pageSize
If returnCustomers.Count = 0 Then Return Nothing
Return returnCustomers
End Function
Consulte também
Referência
Cláusula Select (Visual Basic)
A partir da cláusula (Visual Basic)
Cláusula Order By (Visual Basic)
Cláusula Take While (Visual Basic)
Conceitos
Introdução ao LINQ no Visual Basic