Simple solution
Code
# Code
```csharp []
public class Solution {
    public int AreaOfMaxDiagonal(int[][] dimensions) {
        double max = 0;
        int maxArea = 0;
        for (int i = 0; i < dimensions.Length; i++) {
            int l = dimensions[i][0];
            int w = dimensions[i][1];
            double d = Math.Sqrt(l*l+w*w);

            if (d > max) {
                max = d;
                maxArea = dimensions[i][0]*dimensions[i][1];
            }
            else if (d == max) {
                if (maxArea < dimensions[i][0]*dimensions[i][1]) {
                    maxArea = dimensions[i][0]*dimensions[i][1];
                }
            }
        }

        return maxArea;
    }
}
```
['C#']