CODEWITHSUNDEEP
c#sizemarshalling
user2320928
user2320928

Reputation: 309

C# Marshal.SizeOf

I am using Marshal.SizeOf to know the size of my stucture:

struct loginStruct
{
    public string userName;
    public string password;

    public loginStruct(string userName, string password)
    {
        this.userName = userName;
        this.password = password;
    }
}

Here is the use of this function:

int len = Marshal.SizeOf(typeof(loginStruct));

I got 2 programs. In one program len is equals to 8. In the other it equals to 16. It is the same struct. Why I got that differece?

Upvotes: 5

Views: 5126

Answers (3)

Jon Hanna
Jon Hanna

Reputation: 113272

Methods don't affect the size given, so effectively we're talking about:

struct loginStruct
{
    public string userName;
    public string password;
}

That struct has two reference type fields. As such, it has two fields in the memory which refer to objects on the heap, or to null.

All reference type fields are 4 bytes in 32-bit .NET and 8 bytes in 64-bit .NET.

Hence the size would be 4 + 4 = 8 in 32-bit .NET or 8 + 8 = 16 in 64-bit .NET.

Upvotes: 5

Bassam Alugili
Bassam Alugili

Reputation: 17003

It is depending on the machine and on the build configuration. As @Joey said AnyCPU or 64-Bit

There are some tricks to avoid this problem:

For example you can check:

  • The application type Environment.Is64BitOperatingSystem

  • The size of IntPtr changes on 32 and 64

  • using System.Runtime.InteropServices.Marshal.SizeOf(typeof(Win32DeviceMgmt.SP_DEVINFO_DATA)

Upvotes: 1

Joey
Joey

Reputation: 354546

I'd guess one program is compiled for AnyCPU (which on a 64-bit platform will be 64-bit) and one for 32-bit.

Upvotes: 10

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