在VB.NET中，可以使用Marshal类的PtrToStructure方法和StructureToPtr方法来实现结构体和字节数组之间的相互转换。
以下是一个示例代码：
```vb
Imports System.Runtime.InteropServices
Public Structure MyStruct
Public Field1 As Integer
Public Field2 As Double
End Structure
Public Class Program
Public Shared Sub Main()
' 创建一个结构体实例
Dim myStruct As New MyStruct()
myStruct.Field1 = 10
myStruct.Field2 = 3.14
' 将结构体转换为字节数组
Dim byteSize As Integer = Marshal.SizeOf(myStruct)
Dim byteArray(byteSize - 1) As Byte
Dim structPtr As IntPtr = Marshal.AllocHGlobal(byteSize)
Marshal.StructureToPtr(myStruct, structPtr, False)
Marshal.Copy(structPtr, byteArray, 0, byteSize)
Marshal.FreeHGlobal(structPtr)
' 将字节数组转换回结构体
Dim newStruct As MyStruct = New MyStruct()
structPtr = Marshal.AllocHGlobal(byteSize)
Marshal.Copy(byteArray, 0, structPtr, byteSize)
newStruct = Marshal.PtrToStructure(structPtr, GetType(MyStruct))
Marshal.FreeHGlobal(structPtr)
' 输出转换后的结构体字段值
Console.WriteLine("Field1: " & newStruct.Field1)
Console.WriteLine("Field2: " & newStruct.Field2)
End Sub
End Class
```
运行以上代码，将会输出：
```
Field1: 10
Field2: 3.14
```
这样就实现了结构体和字节数组之间的相互转换。