Snippets

Alex Darby Compare Struct Instances (note: if you need to do this you should really be using a class)

Updated by Alex Darby
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File snippet.txt Modified

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-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+using System;
 
 namespace structRefChecker
 {
 	{
 		static uint s_structIdGenerator = 0;
 
-		private uint	m_structId;
-		public int		m_someValue;
+		private readonly	uint	m_structId;
+		public				int		m_someValue;
 
 		public TestStruct( int value )
 		{
 			m_structId	= s_structIdGenerator++;
 		}
 
-		public static bool IsSameInstance( TestStruct one,  TestStruct two )
+		public static bool StructIdsMatch( TestStruct one,  TestStruct two )
 		{
 			return ( one.m_structId == two.m_structId );
 		}
+
+		// need to allow unsafe code for this to compile. In Visual studio this is: Project -> <projectname> properties -> Build -> [x] allow unsafe code
+		public unsafe static bool AreSameInstance( ref TestStruct one, ref TestStruct two )
+		{	
+			fixed( TestStruct* pone = &one, ptwo = &two )
+			{
+				return pone == ptwo;
+			}
+		}
 	}
 
 	
 	{
 		static void ProcessTestStructs( ref TestStruct one, ref TestStruct two )
 		{
-			if( TestStruct.IsSameInstance( one, two ) )
-			{
-				Console.WriteLine( "one and two are the same instance" );
-				return;
-			}
-				Console.WriteLine( "one and two are different instances" );
-		}
+			Console.WriteLine( string.Format( "one and two have {0} ids", TestStruct.StructIdsMatch( one, two )?"the same":"different" ) );
+			Console.WriteLine( string.Format( "one and two are {0}", TestStruct.AreSameInstance( ref one, ref two )?"the same":"different" ) );
+		}			
 
 		static void Main( string[] args )
 		{
 			ProcessTestStructs( ref testOne, ref testOne ); 
 			ProcessTestStructs( ref testTwo, ref testTwo ); 
 
+			// shortcoming of the id method - can'tr prevent or overload assignment of struct in C#
+			testOne = testTwo;
+
+			ProcessTestStructs( ref testOne, ref testTwo ); 
+
+
 			Console.ReadKey();
 		}
 	}
-}
+}
Created by Alex Darby
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File snippet.txt Added

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+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace structRefChecker
+{
+	public struct TestStruct
+	{
+		static uint s_structIdGenerator = 0;
+
+		private uint	m_structId;
+		public int		m_someValue;
+
+		public TestStruct( int value )
+		{
+			m_someValue	= value;
+			m_structId	= s_structIdGenerator++;
+		}
+
+		public static bool IsSameInstance( TestStruct one,  TestStruct two )
+		{
+			return ( one.m_structId == two.m_structId );
+		}
+	}
+
+	
+
+	class Program
+	{
+		static void ProcessTestStructs( ref TestStruct one, ref TestStruct two )
+		{
+			if( TestStruct.IsSameInstance( one, two ) )
+			{
+				Console.WriteLine( "one and two are the same instance" );
+				return;
+			}
+				Console.WriteLine( "one and two are different instances" );
+		}
+
+		static void Main( string[] args )
+		{
+			var testOne = new TestStruct( 1 );
+			var testTwo = new TestStruct( 2 );
+
+			ProcessTestStructs( ref testOne, ref testTwo ); 
+			ProcessTestStructs( ref testOne, ref testOne ); 
+			ProcessTestStructs( ref testTwo, ref testTwo ); 
+
+			Console.ReadKey();
+		}
+	}
+}
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