连接未关闭是连线.open（）.. visual basic 2008 express edition中的警告 [英] the connection was not closed is the warning in the line connect.open().. visual basic 2008 express edition

问题描述

Private Sub txtusername_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtusername.TextChanged
        username = txtusername.Text
        connect.Open()
        ds.Clear()
        da = New OleDb.OleDbDataAdapter("SELECT * FROM tbluser", connect)
        da.Fill(ds, "tbluser")
        Dim dv As New DataView(ds.Tables("tbluser"))
        dv.RowFilter = "username= '" & username & "'"
        DataGridView1.DataSource = dv
        connect.Close()


    End Sub

推荐答案

将此替换为con.open（）和con.Close（）

Replace this instead of con.open() and con.Close()

if(con.state==ConnectionState.Closed)
{
con.open();
}

if(con.state==ConnectionState.Open)
{
con.Close();
}

错误，因为您的连接未关闭但您正在尝试打开它。

The Error because your Connection is not closed but you are trying to open it.

DataAdapter 自动打开和关闭连接。无需明确打开连接。



参考 - OleDbDataAdapter构造函数（String，OleDbConnection） [ ^ ]

DataAdapter automatically opens and closes the connection. No need to explicitly open the connection.

Reference - OleDbDataAdapter Constructor (String, OleDbConnection)[^]

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