VB.NET读取DataGridView指定单元格值触发索引越界错误，求解决方案

我需要读取3列3行DataGridView中指定单元格（示例为2x2位置）的值，尝试了以下代码后，Visual Studio抛出错误：

"mscorlib.dll中发生未处理的'System.ArgumentOutOfRangeException'异常"
附加信息："索引超出范围。必须为非负值且小于集合大小。"

我的代码： #

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

    'read array and send to DataGridView

    Dim cella(3, 3) As String

    cella(0, 0) = "Papa"
    cella(0, 1) = "Mamma"
    cella(0, 2) = "Bimbo1"
    cella(0, 3) = "Bimbo2"

    cella(1, 0) = "Bianco"
    cella(1, 1) = "Rosso"
    cella(1, 2) = "Nero"
    cella(1, 3) = "Blu"

    cella(2, 0) = "Firenze"
    cella(2, 1) = "Pisa"
    cella(2, 2) = "Livorno"
    cella(2, 3) = "Empoli"

    cella(3, 0) = "Gatto"
    cella(3, 1) = "Cane"
    cella(3, 2) = "Panda"
    cella(3, 3) = "Macaco"

    For x As Integer = 0 To 3
        DataGridView1.Columns.Add("newColumnName", "Testo")
    Next

    For y As Integer = 0 To cella.GetUpperBound(0)
        DataGridView1.Rows.Add(cella(0, y), cella(1, y), cella(2, y), cella(3, y))
    Next

End Sub

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
    
    'Create MsgBox with the value of the specified cell 
    MsgBox(DataGridView1.SelectedRows.Item(2).Cells(2).Value.ToString())

End Sub

请问为何会出现该错误？如何正确读取指定单元格的值？

错误原因 #

1. SelectedRows集合为空：你用DataGridView1.SelectedRows.Item(2)尝试访问选中行集合的第3个元素，但默认情况下没有行被选中，SelectedRows集合长度为0，直接访问索引2必然触发越界异常。
2. DataGridView实际行列数与预期不符：你的Button1_Click代码中，数组定义为(3,3)（对应4x4的元素），循环添加了4列和4行，但你预期的是3列3行，索引逻辑混乱。

正确实现方式 #

1. 直接读取指定位置的单元格 #

不需要依赖选中行，直接通过Rows和Cells的索引访问（注意：DataGridView的行、列索引从0开始，2x2位置对应第3行第3列）：

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
    ' 先判断目标行列是否存在，避免越界
    If DataGridView1.Rows.Count > 2 AndAlso DataGridView1.Columns.Count > 2 Then
        Dim cellValue = DataGridView1.Rows(2).Cells(2).Value
        ' 判断单元格是否为空
        If cellValue IsNot Nothing Then
            MsgBox(cellValue.ToString())
        Else
            MsgBox("该单元格为空")
        End If
    Else
        MsgBox("指定位置的行或列不存在")
    End If
End Sub

2. 修正DataGridView的初始化代码（如果确实需要3列3行） #

调整数组和循环逻辑，创建符合预期的3列3行表格：

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    ' 定义3x3的数组，索引范围0-2
    Dim cella(2, 2) As String

    cella(0, 0) = "Papa"
    cella(0, 1) = "Mamma"
    cella(0, 2) = "Bimbo1"

    cella(1, 0) = "Bianco"
    cella(1, 1) = "Rosso"
    cella(1, 2) = "Nero"

    cella(2, 0) = "Firenze"
    cella(2, 1) = "Pisa"
    cella(2, 2) = "Livorno"

    ' 添加3列
    For x As Integer = 0 To 2
        DataGridView1.Columns.Add($"Column{x}", $"列{x+1}")
    Next

    ' 添加3行
    For y As Integer = 0 To cella.GetUpperBound(0)
        DataGridView1.Rows.Add(cella(y, 0), cella(y, 1), cella(y, 2))
    Next
End Sub

内容的提问来源于stack exchange，提问作者Marco Giglio