Vb.net VB中的For循环

我有一个5乘5的矩阵，我想填充，我想把它简化成for循环

据我所知，我需要2个for循环来完成这项任务

我对VB还是很陌生，希望你能理解

    Dim x(4, 4) As Char

    x(0, 0) = Mid(key, 1, 1)
    x(0, 1) = Mid(key, 2, 1)
    x(0, 2) = Mid(key, 3, 1)
    x(0, 3) = Mid(key, 4, 1)
    x(0, 4) = Mid(key, 5, 1)
    x(1, 0) = Mid(key, 6, 1)
    x(1, 1) = Mid(key, 7, 1)
    ....
    x(4, 4) = Mid(key, 25, 1)

---

试着这样做：

Dim x As Integer
Dim y As Integer
Dim myMatrix(4, 4) As Char

For x = 0 To 4
    For y = 0 To 4
        myMatrix(x, y) =  Mid(key, (x * 5) + y + 1, 1)
    Next
Next