2D字典阵列-复制

让我们告诉我们我有2D字典阵列：

public Dictionary<int, string>[,] mat = new Dictionary<int, string>[3, 5]
{
  { new Dictionary<int, string>(), new Dictionary<int, string>(), new Dictionary<int, string>() },
  { new Dictionary<int, string>(), new Dictionary<int, string>(), new Dictionary<int, string>() },
  { new Dictionary<int, string>(), new Dictionary<int, string>(), new Dictionary<int, string>() },
  { new Dictionary<int, string>(), new Dictionary<int, string>(), new Dictionary<int, string>() },           
  { new Dictionary<int, string>(), new Dictionary<int, string>(), new Dictionary<int, string>() }
}

我需要将复制到另一个。我想尽了办法
类似于：

matNew = mat;

但当我更改第一个时，它会自动更改第二个
我真的不知道该怎么做。

var matNew = new Dictionary<int, string>[mat.GetLength(0), mat.GetLength(1)];
for (int i = 0; i < mat.GetLength(0); ++i)
    for (int j = 0; j < mat.GetLength(1); ++j)
        matNew[i, j] = new Dictionary<int, string>(mat[i, j]);