vb.net常用語句 vbnet using

VB.NET語句中continue while的用法

VB.NET 2005,已經實現了continue語法，具體是這樣操作：

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如果 Continue 語句在 Do...Loop 循環(huán)中，請將該語句更改為 Continue Do。

如果 Continue 語句在 For...Next 循環(huán)中，請將該語句更改為 Continue For。

如果 Continue 語句在 While...End While 循環(huán)中，請將該語句更改為 Continue While。

否則，請移除 Continue 語句。

用法：

For i As Integer = 0 To 100

' If i = 50 跳過 Console.Writeline statement

If i = 50 Then Continue For

Console.WriteLine(i.ToString)

Next

' Do While using Continue statement.

Dim ii As Integer = 1

Do While ii 100

ii += 1

' If ii = 50 跳過 Console.Writeline statement

If ii = 50 Then Continue Do

Console.WriteLine(ii.ToString)

Loop

' While using Continue statement.

Dim iii As Integer = 1

While iii 100

iii += 1

' If iii = 50 跳過 Console.Writeline statement

If iii = 50 Then Continue While

Console.WriteLine(iii.ToString)

End While

vB.Net if 語句

DT.Rows.ToString未必是指結果集中的所有數據，也許只是一行中所有的，或是一列中所有的

保險起見，可以一格格枚舉

dim a as boolean=true

Dim row As DataRow

For Each row In DT.Rows

Dim column As DataColumn

For Each column In DT.Columns

if row(column).contains("Agree") then a=false

Next column

Next row

if a then

Me.rblAgReject.Items(0).Enabled = False

else

Me.rblAgReject.Items(0).Enabled = True

end if

VB中的CASE語句

在VB.NET中VB.NET CASE語句就是比較常用的一種，下面是詳細的介紹和代碼的演示：

1、可以用 Select...Case 語句來替換 If...Then...Else 語句，所不同的是If 和 ElseIf 語句可在每個語句中計算不同的表達式，而 Select 語句對單個表達式只計算一次，然后將其和不同的值比較。

Function?bonus(ByVal?performance?As?Integer,?_??ByVal?salary?As?Decimal)?As?Decimal??

Select?performance??

Case?1??

Return?salary?*?0.1??

Case?2??

Return?salary?*?0.3??

Case?3??

Return?salary?*?0.7??

Case?4??

Return?salary?*?0.9??

Case?5??

Return?salary?*?1.2??

End?Select??

End?Function

2、VB.NET Case語句可包含多個值和某個范圍的值，代碼案例如下：

Function?bonus(ByVal?performance?As?Integer,?_??ByVal?salary?As?Decimal)?As?Decimal??

Select?performance??

Case?1??

Return?salary?*?0.1??

Case?2,3??

Return?salary?*?0.3??

Case?3?To?7??

Return?salary?*?0.7??

Case?8?To?9??

Return?salary?*?0.9??

Case?Is?=?15??

Return?salary?*?1.2??

Case?Else??

Return?0??

End?Select??

End?Function

高分求.net里vb語法操作數據庫基本語句

Dim Cnn As New Data.OleDb.OleDbConnection

Dim DbAdapter As New Data.OleDb.OleDbDataAdapter

Dim Cmd As New Data.OleDb.OleDbCommand

Dim dsAll As New Data.DataSet

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

Cnn.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=E:\webapp\test\web.mdb"

Cmd.Connection = Cnn

End Sub

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click

'插入

Cmd.CommandText = "insert into main (about) values ('" + TextBox1.Text + "')"

UpdateTable()

End Sub

Protected Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button2.Click

'修改

Dim ids As Integer

ids = 1

Cmd.CommandText = "update main set about='" + TextBox1.Text + "' where id=" + ids.ToString()

UpdateTable()

End Sub

Protected Sub Button3_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button3.Click

'刪除

Dim ids As Integer

ids = 1

Cmd.CommandText = "delete from main where id=" + ids.ToString()

UpdateTable()

End Sub

Public Sub UpdateTable()

Dim Trans As Data.OleDb.OleDbTransaction

Try

Cnn.Open()

Trans = Cnn.BeginTransaction()

Try

Cmd.Transaction = Trans

Cmd.ExecuteNonQuery()

Trans.Commit()

Catch

Trans.Rollback()

Finally

If (Cnn.State = System.Data.ConnectionState.Open) Then

Cnn.Close()

End If

End Try

Catch

'error message

End Try

End Sub

Protected Sub Button4_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button4.Click

'顯示

Cmd.CommandText = "select id, about from main"

DbAdapter.SelectCommand = Cmd

DbAdapter.Fill(dsAll, "table1")

If (dsAll.Tables("table1").Rows.Count 0) Then

TextBox1.Text = dsAll.Tables("table1").Rows(0)("about")

Else

TextBox1.Text = ""

End If

End Sub

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