非数据源填充DataGridView结合TextBox搜索触发对象引用错误求助

错误根源 #

触发空引用异常的核心原因有两个：

• 部分单元格的Value为Nothing（空值），直接调用.ToString()会抛出异常
• 未绑定数据源的DataGridView默认开启AllowUserToAddRows，最后一行是空白的待添加行，该行所有单元格值均为Nothing

修复后的代码 #

Private Sub btnApply_Click(sender As Object, e As EventArgs) Handles btnApply.Click
    Dim temp As Integer = 0
    ' 清空之前的黄色高亮，避免残留
    For Each row As DataGridViewRow In DataGridView1.Rows
        For Each cell As DataGridViewCell In row.Cells
            cell.Style.BackColor = DataGridView1.DefaultCellStyle.BackColor
        Next
    Next

    ' 遍历行时跳过最后一行的空白新行（仅当允许添加行时）
    For i As Integer = 0 To DataGridView1.RowCount - 1 - If(DataGridView1.AllowUserToAddRows, 1, 0)
        For j As Integer = 0 To DataGridView1.ColumnCount - 1
            Dim cellValue As String = ""
            ' 先判断单元格值是否非空，再转换为字符串
            If DataGridView1.Rows(i).Cells(j).Value IsNot Nothing Then
                cellValue = DataGridView1.Rows(i).Cells(j).Value.ToString()
            End If

            If cellValue = txtGridSearch.Text Then
                temp = 1
                DataGridView1.Rows(i).Cells(j).Style.BackColor = Color.Yellow
            End If
        Next
    Next

    If temp = 0 Then
        MsgBox("Item not found")
    End If
End Sub

关键改动说明 #

• 空值防护：先检查单元格Value是否不为Nothing，再执行ToString()操作，避免空引用
• 跳过空白新行：根据AllowUserToAddRows状态，自动跳过最后一行的空白待添加行
• 重置高亮状态：每次搜索前清空之前的黄色背景，避免历史高亮残留

内容的提问来源于stack exchange，提问作者Lord45