. Net (C #): emit creates a dynamic method with ref/out

Update:

For the out parameter, we recommend that you read this article:

. Net (C #): more thorough understanding of out parameters from Il and Reflection emit

This document describes how to create two dynamic methods using the dynamicmethod type, including the ref and out parameters.

First, let's look at a simple method:

Static int add (ref int I, int count)

{

Return I + = count;

}

Let's create a dynamic method to execute the above function and then call it.

 

Code:

// + Using system. reflection;

// + Using system. reflection. emit;

VaR dynamicmethod = new dynamicmethod ("", typeof (INT), new type [] {typeof (INT). makebyreftype (), typeof (INT )});

 

Ilgenerator ilgen = dynamicmethod. getilgenerator ();

 

// I stack, Stack: I

Ilgen. emit (Opcodes. ldarg_0 );

// Copy I. The top I is used to obtain the specified integer. STACK: I, I

Ilgen. emit (Opcodes. DUP );

// Obtain the integer I represents. STACK: I, * I

Ilgen. emit (Opcodes. ldind_i4 );

// Count to stack. STACK: I, * I, count

Ilgen. emit (Opcodes. ldarg_1 );

// Add operation. STACK: I, * I + count

Ilgen. emit (Opcodes. Add );

// Assign a value. STACK: * I + count

Ilgen. emit (Opcodes. stind_i4 );

// Re-apply the updated I to the stack

Ilgen. emit (Opcodes. ldarg_0 );

// Obtain * I

Ilgen. emit (Opcodes. ldind_i4 );

 

// End

Ilgen. emit (Opcodes. Ret );

 

Next, call this dynamic method:

// Parameters:

VaR I =-3;

VaR COUNT = 10;

VaR Arg = new object [] {I, Count };

 

// Call a dynamic method

Int result = (INT) dynamicmethod. Invoke (null, ARG );

 

// Output result

Console. writeline (result );

Console. writeline (ARG [0]);

 

Output:

7

7

OK. The return value and the first parameter result are both 7.

 

Next let's take a look at the out parameter:

You will create a method like this:

Static void outobject (Out object OBJ)

{

OBJ = "hehe ";

}

 

Code:

// + Using system. reflection;

// + Using system. reflection. emit;

 

VaR dynamicmethod = new dynamicmethod ("", null, new type [] {typeof (object). makebyreftype ()});

 

// Set the ref parameter to out. (In fact, this program will be successfully executed without it)

Dynamicmethod. defineparameter (1, parameterattributes. Out, "OBJ ");

 

Ilgenerator ilgen = dynamicmethod. getilgenerator ();

 

// Import OBJ to stack

Ilgen. emit (Opcodes. ldarg_0 );

// Add hehe to the stack

Ilgen. emit (Opcodes. ldstr, "hehe ");

// Assign a value

Ilgen. emit (Opcodes. stind_ref );

// Exit

Ilgen. emit (Opcodes. Ret );

 

 

// Parameters:

VaR Arg = new object [] {null };

 

// Call a dynamic method

Dynamicmethod. Invoke (null, ARG );

 

// Output result

Console. writeline (ARG [0]);

Output:

Hehe