Question

如何在vb.net中使用for循环，如

dim start as integer
Dim customers as New List(Of Customers)

Customers=dataAcess.GetCustomers()

For each start=500 in  Customers.count
  'Do something here'
Next

我想为每500位客户处理一些数据..请帮忙

Answer 1

尝试以下

For Each current In customers
  '' // Do something here 
  Console.WriteLine(current.Name)
Next

Answer 2

首先，如果您要在下一行为参考分配不同的列表，请不要创建New客户列表。那有点蠢。这样做：

Dim customers As List(Of Customer) = dataAccess.GetCustomers()

然后，对于循环，您需要一个简单的“For”循环而不是每个循环。不要忘记在列表结尾之前停止：

For i As Integer = 500 To Customers.Count -1 
    'do something with Customers(i) here
Next i

如果您使用的是Visual Studio 2008，您也可以这样写：

For each item As Customer in  Customers.Skip(500)
   'Do something with "item" here
Next

Answer 3

'这将从500开始并处理到结束....

for start as integer = 500 to Customers.Count

'process customer....
customer = Customers(start)

Next

迭代整个列表：

for each cust as Customer in Customers

Next

一个注意事项...... VB不区分大小写，您的示例代码似乎使用小写和大写客户

Answer 4

这样的事情： -

Dim customers as New List(Of Customer)

Customers=dataAcess.GetCustomers()

For Each customer AS Customer in  Customers
   '' // do something with the customer object
Next

修改

听起来您想要选择N个项目中的500个或者接下来的500个项目。您可以使用LINQ扩展方法.Take和/或.Skip来实现此目的。然后使用ToList创建列表。 E.g： -

Dim customers as List(Of Customer) customers = dataAccess.GetCustomers().Skip(500).Take(500).ToList()

如果您只想通过客户进行枚举，那么您可以省去ToList（）。

Answer 5

您可以尝试：

    For i As Integer = 500 To (customers.Count -1)
        ''do something
    Next

或者

    For i As Integer = 0 To (customers.Count - 1) step 500
        ''do something
    Next

Answer 6

Dim start as Integer
Dim customers as New List(Of Customers)

Customers = dataAcess.GetCustomers()

For i as Integer = start to Customers.count Step 500
    Debug.Print Customers(i).someProperty
    Do something here
Next i

我认为你需要使用Customer索引和Steps in 500s。这只会处理客户（开始），客户（开始+ 500），客户（开始+ 1000）等，而不是所有客户。这是你想要的吗？

Answer 7

我不确定你要做什么，但也许你可以试试这个：

Dim count As Integer = 0
Const MAX_CUSTOMERS As Integer = 500
Dim customers As List(Of Customers) = dataAcess.GetCustomers()

For Each c As Customer In customers
    'do stuff here'
    c.Name = "Billy"
    count+=1

    If count = MAX_CUSTOMERS Then Exit For
Next

它无论如何都不优雅，但它有意义，它会起作用。

Answer 8

显然，品种并不缺乏。我不认识你的“DataAcess”对象类型，但如果你可以将该表作为Recordset（即一个SQL表）拉出来，那么试试这个。（完成后不要忘记返回记录集）

Option Explicit

Dim Customers As Recordset
Set Customers=currentdb.openrecordset("???")

While Customers.EOF=False
   'do stuff here using the recordset object
   'i.e. Customers.Fields("Name")="Billy"
   Customers.MoveNext
Wend

对于vb.net中的每个循环

8 个答案: