mysql - 你调用的对象是空的

Question

 Private Sub btnSelectAsset_Click(sender As Object, e As EventArgs) Handles btnSelectAsset.Click
    MySqlConn = New MySqlConnection
    MySqlConn.ConnectionString =
    "server=localhost;userid=root;password= ;database=myma"
    Dim SDA As MySqlDataAdapter
    Dim dbDataSet As New DataTable
    Dim bSource As New BindingSource

    Try
        MySqlConn.Open()
        COMMAND.Connection = MySqlConn
        SDA = New MySqlDataAdapter("select * from myma.user", MySqlConn)
        dbDataSet = New DataTable
        SDA.Fill(dbDataSet)
        DataGridView1.DataSource = dbDataSet
        MySqlConn.Close()

    Catch ex As Exception
        MessageBox.Show(ex.Message)
    Finally
        MySqlConn.Dispose()
    End Try
End Sub

object reference not set to an instance of an object.

调试时出现上述错误。您能帮我纠正这个问题吗？

Answer 1

尝试这个工作示例:

Private Sub btnSelectAsset_Click(sender As Object, e As EventArgs) Handles btnSelectAsset.Click
    Dim dbConn = New MySqlConnection
    Dim dbDataTable = New DataTable

    dbConn.ConnectionString = "server=localhost;userid=root;password= ;database=myma"

    Try
        dbConn.Open()
        If (dbConn.State = ConnectionState.Open) Then
            Dim dbAdapter = New MySqlDataAdapter("select * from myma.user", dbConn)
            dbAdapter.Fill(dbDataTable)
            DataGridView1.DataSource = dbDataTable
            dbConn.Close()
        End If
    Catch ex As Exception
        MessageBox.Show(ex.Message)
    Finally
        dbConn.Dispose()
    End Try
End Sub

VB2010Ex 和 .NET 4 客户端配置文件。