Question

我想创建一个可以注册个人信息的应用程序。但我在gridview中更新/编辑数据时遇到问题。下面是我创建的代码集。

Imports System.Data.SqlClient
Public Class Form1
Dim connectionString As String
Dim cnn As SqlConnection
Dim cmd As SqlCommand
Dim sql As String

下面的

是我的ADD声明，它可以正常工作

Private Sub btnADD_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnADD.Click

    connectionString = "Data Source=XXXX;Initial Catalog=XXXX;User ID=XXXX;Password=XXXX"
    cnn = New SqlConnection(connectionString)
    Try
        cnn.Open()
        cmd = New SqlCommand("INSERT INTO tbl_info (ID,Name) VALUES (@ID,@Name)")
        cmd.Connection = cnn
        With cmd.Parameters
            .AddWithValue("ID", txtID.Text)
            .AddWithValue("Name", txtName.Text)
        End With
        cmd.ExecuteNonQuery()
        MsgBox("has been inserted successfully")

    Catch ex As Exception
        MsgBox(ex.Message())
    End Try


    txtID.Clear()
    txtName.Clear()
End Sub

下面是gridview witch链接到我的数据库

  Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    'TODO: This line of code loads data into the 'TestDataSet.tbl_info' table. You can move, or remove it, as needed.
    Me.Tbl_infoTableAdapter.Fill(Me.TestDataSet.tbl_info)

End Sub

下面是我的更新声明，我很难弄清楚出了什么问题。

 Private Sub btnEdit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEdit.Click
    cnn = New SqlConnection(connectionString)
    If Not cnn.State = ConnectionState.Open Then
        cnn.Open()
    End If

    Try
        cmd = New SqlCommand("Update tble_info set Name = @Name Where ID = @ID)")
        cmd.Connection = cnn
        With cmd.Parameters
            .AddWithValue("Name", txtName.Text)
            .AddWithValue("ID", txtID.Text)
        End With
        cmd.ExecuteNonQuery()
        MsgBox("has been update successfully")
    Catch ex As Exception
        MsgBox(ex.Message())
    End Try
   End Sub
End Class

这是我执行程序时遇到的错误

InvalidOperationExeption was unhadled
The connectionString property has not been initialize

指向cnn.open（）

Answer 1

我不确定到底出了什么问题，我只能想象connectionStringI在某种程度上Null当你试图使用它时，我认为每个关闭连接都是好的做法。你完成它的时间。

因此，当您获取数据而不是像现在一样打开连接时，请执行类似

的操作

With New SqlConnection(connectionString)
    Try
        .Open()
        ' Do Stuff
    Catch
        ' Handle your exception
    Finally
         .Close()
    End Try
End With

这样你的连接将永远关闭，你不必担心检查它是否已经打开。

更新

我冒昧地按照我的方式重写你的代码。你可以试一试，看看它是否适合你/

您连接字符串属性：

Private ReadOnly Property connectionString As String
    Get
        Return "Data Source=XXXX;Initial Catalog=XXXX;User ID=XXXX;Password=XXXX"
    End Get
End Property

插入数据的子：

Private Sub btnADD_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnADD.Click

    Dim transaction As SqlTransaction = Nothing

    With New SqlConnection(connectionString)
        Try
            Call .Open()
            transaction = .BeginTransaction()
            With .CreateCommand()
                .Transaction = transaction
                .CommandText = "INSERT INTO [tbl_info] ([ID], [Name]) VALUES (@ID,@Name);"
                With .Parameters
                    .AddWithValue("ID", txtID.Text)
                    .AddWithValue("Name", txtName.Text)
                End With
                Call .ExecuteNonQuery()
                Call transaction.Commit()
                Call MessageBox.Show("has been inserted successfully")
            End With
        Catch ex As Exception
            Call transaction.Rollback()
            Call MessageBox.Show(ex.Message, "Error")
        Finally
            Call .Close()
        End Try
    End With

    Call txtID.Clear()
    Call txtName.Clear()

End Sub

更新数据的子：

Private Sub btnEdit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEdit.Click

    Dim transaction As SqlTransaction = Nothing

    With New SqlConnection(connectionString)
        Try
            Call .Open()
            transaction = .BeginTransaction()
            With .CreateCommand()
                .Transaction = transaction
                .CommandText = "UPDATE [tble_info] SET [Name]=@Name WHERE [ID]=@ID;"
                With .Parameters
                    .AddWithValue("Name", txtName.Text)
                    .AddWithValue("ID", txtID.Text)
                End With
                Call .ExecuteNonQuery()
                Call transaction.Commit()
                Call MessageBox.Show("has been update successfully")
            End With
        Catch ex As Exception
            Call transaction.Rollback()
            Call MessageBox.Show(ex.Message, "Error")
        Finally
            Call .Close()
        End Try
    End With

End Sub

如果将连接字符串设置为（只读）属性，假设它没有更改，那么在使用它时，您不必担心它是否具有值。然后你需要担心的是确保连接字符串是正确的。

请注意，我没有测试过这段代码，但它应该像我想的那样工作。

无法更新/编辑数据库

1 个答案: