Thanks Barry for your informative input.

Hi Praveen,

Thank you for your post.

As Barry pointed out, a good expiration policy of is key to your caching
system.

To get memory size of a single type, we can use Type.TypeHandle to get the
basic instance size of this type. You can use following code to test:

=====
using System;

class SimpleClass
{
   private byte b1 = 1;                // 1 byte
   private byte b2 = 2;                // 1 byte
   private byte b3 = 3;                // 1 byte
   private byte b4 = 4;                // 1 byte
   private char c1 = 'A';              // 2 bytes
   private char c2 = 'B';              // 2 bytes
   private short s1 = 11;              // 2 bytes
   private short s2 = 12;              // 2 bytes
   private int i1 = 21;                // 4 bytes
   private long l1 = 31;               // 8 bytes
   private string str = "MyString"; // 4 bytes (only OBJECTREF)

   //Total instance variable size = 28 bytes

   static void Main()
   {
       SimpleClass simpleObj = new SimpleClass();
       int basicInstanceSize = GetBasicInstanceSize(simpleObj.GetType());
       Console.Write(basicInstanceSize);
   }

   /// <summary>
   /// Gets the size of instances of the given type. It is the sum of:
   ///   - a fixed object overhead (8 bytes)
   ///   - the sizes of all the instance fields (note: may include padding)
   /// For more information see:
   ///   -
http://msdn.microsoft.com/msdnmag/issues/05/05/JITCompiler/default.aspx
   ///   -
http://msdn.microsoft.com/msdnmag/issues/05/05/JITCompiler/default.aspx?fig=
true#fig9
   /// </summary>
   /// <param name="type">A type.</param>
   /// <returns>Size in bytes of instances of the given type.</returns>
   private static int GetBasicInstanceSize(Type type)
   {
       // Read the first 8 bytes (=2 ints) of the MethodTable. The basic
instance size is the second int.
       IntPtr methodTableIntPtr = IntPtr.Zero;
       try
       {
           methodTableIntPtr = type.TypeHandle.Value;
           int[] methodTableData = new int[2];
           System.Runtime.InteropServices.Marshal.Copy(methodTableIntPtr,
methodTableData, 0, 2);
           int basicInstanceSize = methodTableData[1];
           return basicInstanceSize;
       }
       finally
       {
           if (methodTableIntPtr != IntPtr.Zero)
               
System.Runtime.InteropServices.Marshal.Release(methodTableIntPtr);
       }
   }
}
=====

Hope this helps. Please feel free to post here if anything is unclear.

Sincerely,
Walter Wang (wawang@online.microsoft.com, remove 'online.')
Microsoft Online Community Support

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