To get the total virtual memory of the system in C# and VB.NET you can use the following snippet.
Sample C#
Console.WriteLine("Total Virtual Memory (bytes) in System: {0}", new Microsoft.VisualBasic.Devices.ComputerInfo().TotalVirtualMemory);
Sample VB.NET
Console.WriteLine("Total Virtual Memory (bytes) in System: {0}", New Microsoft.VisualBasic.Devices.ComputerInfo().TotalVirtualMemory)