关于vb.net删除实例的信息

vb.net 类实例的销毁

无代码无真相！

话说，应该看你这个实例a是作用域的变量，如果仅仅是在函数A中定义的局部变量，那么应该会在函数运行完成的时候自动销毁的。这个应该是变量的生存期问题。

但是，根据你所提供的描述来看，你的这个a类应该定义的至少是一个是模块级别的变量，不然，你在函数B中，用另一个b类来引用a实例是无法实现的。因此，我感觉函数A运行完了之后，你的a实例应该并没有销毁，只有等到整个模块被结束的时候才能销毁。

(PS: VB.net没有用过，以上仅仅是基于vb6.0的类模块使用方法所提出的一点参考建议！)

相关问答

Q1: 求 vb.net winform datagridview checkbox多行删除实例

'批量删除信息

Dim flag As Boolean = False '标识是否删除成功

For index = 0 To DataGridView1.Rows.Count - 1

If dgDataGridView1tem("控件名称", index).Value=true Then

Dim orderId As Integer = Integer.Parse(DataGridView1.Item("列名", index).Value)

'调用删除方法

If 类.方法名() Then

flag=True

End If

End If

Next

if flag=true then

messagebox.show("删除成功！")

else

messagebox.show("删除失败！")

当然：类.方法名() 这个方法返回一个布尔值，呵呵，也可以是其它类型，到时候可要变哦

Q2: VB.net怎样全部删除DataGridView的内容？

方法有多种。

可以dataAdapter.Fill到数据表应该，设置几个command，再通过dataAdapter.Update就可以更新数据了。不过表要有一个关键的key吧。

另外一种直观一点：

也需要表有个关键key有就是关键字段。

你datagridview.reomveAt(index)同时执行sqlcommand("delete * From table where keyFild='" key "'")就可以。

参考一个实例，如下：

Private Sub bitDelete_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles bitDelete.Click

Dim oraConn As New OracleConnection()

oraConn.ConnectionString = " data source=数据库名字;user id=账号;password=密码"

oraConn.Open()

Dim id As String = DataGridView1.CurrentRow.Cells(0).Value.ToString().Trim()

Dim queryString = "delete from t where id ='" id号 "'"

Dim adapter As OracleDataAdapter = New OracleDataAdapter(queryString,oraConn)

Dim mark As DataSet = New DataSet

adapter.Fill(mark, "Mark")

MessageBox.Show("删除数据成功!")

Dim adapter As OracleDataAdapter = New OracleDataAdapter("select * from t ORDER BY id", oraConn)

Dim score As DataSet = New DataSet()

adapter.Fill(score , "Score ")

DataGridView1.DataSource = score

DataGridView1.DataMember = score .Tables(0).ToString

oraConn.Close()

End Sub

Q3: 求一个VB.net 增删改查实例 ，哪位大神有空帮我写一下或者有现成的给我一个，，我比较菜又比较急，在线等

Imports System.Data.OleDb

'Imports System.Data.OracleClient

Imports System.Data.SqlClient

'链接Oracle

'cn = New SqlConnection(""Data Source=TNS名称;Persist Security Info=True;User ID=用户名;Password=密码;" ")

'Imports System.Data.OracleClient

'Dim oOracleConn As OracleConnection = New OracleConnection()

'oOracleConn.ConnectionString = ""Data Source=MyOracleDB; User Id=username; Password=passwd; Integrated Security=no; "

'oOracleConn.Open()

'链接SQL Server

'cn = New SqlConnection("Data Source=.;Initial Catalog=Sales;Integrated Security=False;User ID=sa;Password=;")

'链接Access

'cn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" db_path ";Persist Security Info=False")

Public Class Fun_DataBase

Dim cn As OleDbConnection

Dim cm As OleDbCommand

Dim da As OleDbDataAdapter

Dim ds As DataSet

Dim db_path As String = "D:\Documents\Visual Studio 2013\Projects\VBnet1\VBnet1\Resources\Database1.mdb"

Function Fun_sql1(Str_sql As String, V_调用来源 As String) '按指定sql，反馈1个查询值

Try

'Dim cn As New OleDbConnection("Data Source=.;Initial Catalog=Sales;Integrated Security=False;User ID=sa;Password=123456;")

'链接Access

cn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" db_path ";Persist Security Info=False")

cn.Open() 'sql语句执行前，必须打开连接

cm = New OleDbCommand(Str_sql, cn)

cm.ExecuteNonQuery()

Dim strValue As String = cm.ExecuteScalar.ToString

'MessageBox.Show(strValue)

Fun_sql1 = strValue

cn.Close()

Fun_sql1 = True

Catch ex As Exception

MessageBox.Show(V_调用来源 ":执行sql语句失败！" Str_sql)

Fun_sql1 = False

End Try

End Function

Function Fun_sqln(Str_sql As String, V_调用来源 As String) '按指定sql，反馈1行n列查询值

Try

'链接Access

cn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" db_path ";Persist Security Info=False")

cn.Open() 'sql语句执行前，必须打开连接

Dim cmd As New OleDbCommand("select * from grade", cn)

'Dim dr As SqlDataReader

Dim dr As OleDbDataReader

dr = cmd.ExecuteReader()

Dim strDisplay As String = ""

While dr.Read()

Fun_sqln = dr(0).ToString "|"

End While

cn.Close()

Fun_sqln = True

Catch ex As Exception

MessageBox.Show(V_调用来源 ":执行sql语句失败！" Str_sql)

Fun_sqln = False

End Try

'Dim s = Split(F.Fun_sqln("ef"), "|")

'Dim i As Integer

'i = UBound(s)

'For i = 0 To UBound(s)

' MessageBox.Show(s(i))

'Next

End Function

Public Function Fun_sql_exec(Str_sql As String, V_调用来源 As String) '执行指定sql，反馈T|F

Try

'链接Access

cn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" db_path ";Persist Security Info=False")

cn.Open() 'sql语句执行前，必须打开连接

cm = New OleDbCommand(Str_sql, cn)

cm.ExecuteNonQuery()

cn.Close()

Fun_sql_exec = True

Catch ex As Exception

MessageBox.Show(V_调用来源 ":执行sql语句失败！" Str_sql)

Fun_sql_exec = False

End Try

End Function

Q4: vb.net 注册表删除操作 郁闷中……

这不是废话吗，DeleteSubKey只能删除调用实例的子项，并不能直接删除子子项。