VB.Net：如何将DataGridView选中行数据显示到另一窗体文本框？

我帮你梳理下问题所在，以及对应的解决办法：

核心问题分析 #

你的代码之所以没效果，主要有两个关键原因：

1. 数据获取的时机不对 #

你把获取选中行数据的代码放在了CellContentClick事件里，但这个事件只有当你点击DataGridView单元格内的具体内容（比如按钮列的按钮、单元格里的文本）时才会触发。而你的操作流程是先点击选中DataGridView的某一行（可能点击的是行的空白区域或者单元格但没触发CellContentClick），再点击窗体上的编辑按钮——这时候CellContentClick根本没执行，那些公共变量自然都没被赋值，EditPage里当然拿不到数据。

2. 直接访问窗体类的非共享变量存在风险 #

你在EditPage里用Main.id这种方式访问变量，本质是访问Main窗体类的默认实例。但如果你的Main窗体不是通过默认实例创建的（比如代码里用New Main()打开的），那这个默认实例的变量是空的，和你正在操作的那个Main窗体实例完全不是同一个，自然拿不到正确的数据。

具体解决办法 #

我推荐两种更可靠的方案，你可以选一种适合自己的：

方案一：用构造函数直接传递数据（最规范的方式） #

这种方式不需要公共变量，直接在打开编辑窗体时把选中行的数据传过去，避免全局变量的各种问题：

第一步：给EditPage添加带参数的构造函数

在EditPage.vb里添加以下代码：

' 自定义构造函数，接收选中行的所有数据
Public Sub New(id As Integer, firstname As String, lastname As String, birthdate As String, position As String, sex As String, address As String, contact_num As String, email As String)
    ' 必须先调用InitializeComponent()初始化窗体控件
    InitializeComponent()
    
    ' 直接把数据赋值给对应的控件
    firstname_txtbox.Text = firstname
    lastname_txtbox.Text = lastname
    DateTimePicker1.Text = birthdate
    position_txtbox.Text = position
    sex_combo.Text = sex
    address_txtbox.Text = address
    contact_mask.Text = contact_num
    email_txtbox.Text = email
End Sub

第二步：修改Main窗体的编辑按钮点击事件

在Main.vb的Button3_Click事件里，直接获取选中行数据并传递给EditPage：

Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
    ' 先判断是否选中了行
    If tblAttendance.CurrentRow Is Nothing Then
        MessageBox.Show("请先选中一行数据再编辑！", "提示")
        Return
    End If
    
    Dim result As Integer = MessageBox.Show("Are you sure you want to Edit the Info?", "Validation", MessageBoxButtons.YesNoCancel)
    If result = DialogResult.Yes Then
        Dim row As DataGridViewRow = tblAttendance.CurrentRow
        Try
            ' 转换并获取每行的数据（注意处理可能的空值）
            Dim id As Integer = If(row.Cells(0).Value Is DBNull.Value, 0, Convert.ToInt32(row.Cells(0).Value))
            Dim firstname As String = If(row.Cells(1).Value Is DBNull.Value, "", row.Cells(1).Value.ToString())
            Dim lastname As String = If(row.Cells(2).Value Is DBNull.Value, "", row.Cells(2).Value.ToString())
            Dim birthdate As String = If(row.Cells(3).Value Is DBNull.Value, "", row.Cells(3).Value.ToString())
            Dim position As String = If(row.Cells(4).Value Is DBNull.Value, "", row.Cells(4).Value.ToString())
            Dim sex As String = If(row.Cells(5).Value Is DBNull.Value, "", row.Cells(5).Value.ToString())
            Dim address As String = If(row.Cells(6).Value Is DBNull.Value, "", row.Cells(6).Value.ToString())
            Dim contact_num As String = If(row.Cells(7).Value Is DBNull.Value, "", row.Cells(7).Value.ToString())
            Dim email As String = If(row.Cells(8).Value Is DBNull.Value, "", row.Cells(8).Value.ToString())
            
            ' 创建EditPage实例并传递数据
            Dim editForm As New Edit_Page(id, firstname, lastname, birthdate, position, sex, address, contact_num, email)
            editForm.Show()
        Catch ex As Exception
            MessageBox.Show("数据转换出错：" & ex.Message, "错误")
        End If
    ElseIf result = DialogResult.No Then
        MessageBox.Show("Edit Cancelled", "Message")
    End If
End Sub

方案二：改进公共变量的使用方式（如果你坚持用公共变量） #

如果你还是想用公共变量传递数据，需要修改两个地方：

第一步：把数据获取移到SelectionChanged事件

在Main.vb里添加SelectionChanged事件，确保选中行时就更新公共变量：

Private Sub tblAttendance_SelectionChanged(sender As Object, e As EventArgs) Handles tblAttendance.SelectionChanged
    If tblAttendance.CurrentRow IsNot Nothing Then
        Dim row As DataGridViewRow = tblAttendance.CurrentRow
        Try
            ' 处理空值和类型转换
            id = If(row.Cells(0).Value Is DBNull.Value, 0, Convert.ToInt32(row.Cells(0).Value))
            firstname = If(row.Cells(1).Value Is DBNull.Value, "", row.Cells(1).Value.ToString())
            lastname = If(row.Cells(2).Value Is DBNull.Value, "", row.Cells(2).Value.ToString())
            birthdate = If(row.Cells(3).Value Is DBNull.Value, "", row.Cells(3).Value.ToString())
            position = If(row.Cells(4).Value Is DBNull.Value, "", row.Cells(4).Value.ToString())
            sex = If(row.Cells(5).Value Is DBNull.Value, "", row.Cells(5).Value.ToString())
            address = If(row.Cells(6).Value Is DBNull.Value, "", row.Cells(6).Value.ToString())
            contact_num = If(row.Cells(7).Value Is DBNull.Value, "", row.Cells(7).Value.ToString())
            email = If(row.Cells(8).Value Is DBNull.Value, "", row.Cells(8).Value.ToString())
        Catch ex As Exception
            MessageBox.Show("获取选中行数据失败：" & ex.Message, "错误")
        End If
    End If
End Sub

第二步：传递当前Main窗体实例给EditPage

在EditPage.vb里添加一个属性来接收Main窗体实例：

Public Property ParentMainForm As Main ' 这里的Main是你的Main窗体类名

然后修改EditPage的Load事件：

Private Sub Edit_Page_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    If ParentMainForm IsNot Nothing Then
        ' 通过传递过来的实例访问公共变量
        firstname_txtbox.Text = ParentMainForm.firstname
        lastname_txtbox.Text = ParentMainForm.lastname
        DateTimePicker1.Text = ParentMainForm.birthdate
        position_txtbox.Text = ParentMainForm.position
        sex_combo.Text = ParentMainForm.sex
        address_txtbox.Text = ParentMainForm.address
        contact_mask.Text = ParentMainForm.contact_num
        email_txtbox.Text = ParentMainForm.email
    End If
End Sub

最后修改Main窗体的编辑按钮事件：

Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
    If tblAttendance.CurrentRow Is Nothing Then
        MessageBox.Show("请先选中一行数据！", "提示")
        Return
    End If
    
    Dim result As Integer = MessageBox.Show("Are you sure you want to Edit the Info?", "Validation", MessageBoxButtons.YesNoCancel)
    If result = DialogResult.Yes Then
        Dim editForm As New Edit_Page()
        editForm.ParentMainForm = Me ' 传递当前Main窗体的实例
        editForm.Show()
    ElseIf result = DialogResult.No Then
        MessageBox.Show("Edit Cancelled", "Message")
    End If
End Sub

额外注意事项 #

• 建议把DataGridView的SelectionMode属性设置为FullRowSelect，这样点击行的任何区域都会选中整行，方便获取CurrentRow。
• 一定要处理单元格值为DBNull的情况，避免空值转换时抛出异常。

内容的提问来源于stack exchange，提问作者Nikko Tongoy