ILGenerator.EmitWriteLine Method

Definition

Namespace:

System.Reflection.Emit

Assemblies:

netstandard.dll, System.Reflection.Emit.ILGeneration.dll

Helper functions to emit a call to WriteLine() with different types of values.

Overloads

EmitWriteLine(String)	Emits the Microsoft intermediate language (MSIL) to call WriteLine with a string.
EmitWriteLine(FieldInfo)	Emits the Microsoft intermediate language (MSIL) necessary to call WriteLine with the given field.
EmitWriteLine(LocalBuilder)	Emits the Microsoft intermediate language (MSIL) necessary to call WriteLine with the given local variable.

EmitWriteLine(String)

Source:

ILGenerator.cs

Emits the Microsoft intermediate language (MSIL) to call WriteLine with a string.

C#

public virtual void EmitWriteLine(string value);

Parameters

value

String

The string to be printed.

Examples

The code sample below demonstrates the contextual usage of the EmitWriteLine method to write a string to the console in a dynamic method.

C#

using System;
using System.Threading;
using System.Reflection;
using System.Reflection.Emit;

class EmitWriteLineDemo {

   public static Type CreateDynamicType() {
       Type[] ctorParams = new Type[] {typeof(int),
                   typeof(int)};
    
       AppDomain myDomain = Thread.GetDomain();
       AssemblyName myAsmName = new AssemblyName();
       myAsmName.Name = "MyDynamicAssembly";

       AssemblyBuilder myAsmBuilder = myDomain.DefineDynamicAssembly(
                      myAsmName,
                      AssemblyBuilderAccess.Run);

       ModuleBuilder pointModule = myAsmBuilder.DefineDynamicModule("PointModule",
                                    "Point.dll");

       TypeBuilder pointTypeBld = pointModule.DefineType("Point",
                                  TypeAttributes.Public);

       FieldBuilder xField = pointTypeBld.DefineField("x", typeof(int),
                                                      FieldAttributes.Public);
       FieldBuilder yField = pointTypeBld.DefineField("y", typeof(int),
                                                      FieldAttributes.Public);

       Type objType = Type.GetType("System.Object");
       ConstructorInfo objCtor = objType.GetConstructor(new Type[0]);

       ConstructorBuilder pointCtor = pointTypeBld.DefineConstructor(
                                   MethodAttributes.Public,
                                   CallingConventions.Standard,
                                   ctorParams);
       ILGenerator ctorIL = pointCtor.GetILGenerator();

       // First, you build the constructor.
       ctorIL.Emit(OpCodes.Ldarg_0);
       ctorIL.Emit(OpCodes.Call, objCtor);
       ctorIL.Emit(OpCodes.Ldarg_0);
       ctorIL.Emit(OpCodes.Ldarg_1);
       ctorIL.Emit(OpCodes.Stfld, xField);
       ctorIL.Emit(OpCodes.Ldarg_0);
       ctorIL.Emit(OpCodes.Ldarg_2);
       ctorIL.Emit(OpCodes.Stfld, yField);
       ctorIL.Emit(OpCodes.Ret);

       //  Now, you'll build a method to output some information on the
       // inside your dynamic class. This method will have the following
       // definition in C#:
    //  public void WritePoint()

       MethodBuilder writeStrMthd = pointTypeBld.DefineMethod(
                                     "WritePoint",
                             MethodAttributes.Public,
                                             typeof(void),
                                             null);

       ILGenerator writeStrIL = writeStrMthd.GetILGenerator();

       // The below ILGenerator created demonstrates a few ways to create
       // string output through STDIN.

       // ILGenerator.EmitWriteLine(string) will generate a ldstr and a
       // call to WriteLine for you.

       writeStrIL.EmitWriteLine("The value of this current instance is:");

       // Here, you will do the hard work yourself. First, you need to create
       // the string we will be passing and obtain the correct WriteLine overload
       // for said string. In the below case, you are substituting in two values,
       // so the chosen overload is Console.WriteLine(string, object, object).

       String inStr = "({0}, {1})";
       Type[] wlParams = new Type[] {typeof(string),
                     typeof(object),
                     typeof(object)};

       // We need the MethodInfo to pass into EmitCall later.

       MethodInfo writeLineMI = typeof(Console).GetMethod(
                            "WriteLine",
                        wlParams);

       // Push the string with the substitutions onto the stack.
       // This is the first argument for WriteLine - the string one.

       writeStrIL.Emit(OpCodes.Ldstr, inStr);

       // Since the second argument is an object, and it corresponds to
       // to the substitution for the value of our integer field, you
       // need to box that field to an object. First, push a reference
       // to the current instance, and then push the value stored in
       // field 'x'. We need the reference to the current instance (stored
       // in local argument index 0) so Ldfld can load from the correct
       // instance (this one).

       writeStrIL.Emit(OpCodes.Ldarg_0);
       writeStrIL.Emit(OpCodes.Ldfld, xField);

       // Now, we execute the box opcode, which pops the value of field 'x',
       // returning a reference to the integer value boxed as an object.

       writeStrIL.Emit(OpCodes.Box, typeof(int));

       // Atop the stack, you'll find our string inStr, followed by a reference
       // to the boxed value of 'x'. Now, you need to likewise box field 'y'.

       writeStrIL.Emit(OpCodes.Ldarg_0);
       writeStrIL.Emit(OpCodes.Ldfld, yField);
       writeStrIL.Emit(OpCodes.Box, typeof(int));

       // Now, you have all of the arguments for your call to
       // Console.WriteLine(string, object, object) atop the stack:
       // the string InStr, a reference to the boxed value of 'x', and
       // a reference to the boxed value of 'y'.

       // Call Console.WriteLine(string, object, object) with EmitCall.

       writeStrIL.EmitCall(OpCodes.Call, writeLineMI, null);

       // Lastly, EmitWriteLine can also output the value of a field
       // using the overload EmitWriteLine(FieldInfo).

       writeStrIL.EmitWriteLine("The value of 'x' is:");
       writeStrIL.EmitWriteLine(xField);
       writeStrIL.EmitWriteLine("The value of 'y' is:");
       writeStrIL.EmitWriteLine(yField);

       // Since we return no value (void), the ret opcode will not
       // return the top stack value.

       writeStrIL.Emit(OpCodes.Ret);

       return pointTypeBld.CreateType();
   }

   public static void Main() {

      object[] ctorParams = new object[2];

      Console.Write("Enter a integer value for X: ");
      string myX = Console.ReadLine();
      Console.Write("Enter a integer value for Y: ");
      string myY = Console.ReadLine();

      Console.WriteLine("---");

      ctorParams[0] = Convert.ToInt32(myX);
      ctorParams[1] = Convert.ToInt32(myY);

      Type ptType = CreateDynamicType();

      object ptInstance = Activator.CreateInstance(ptType, ctorParams);
      ptType.InvokeMember("WritePoint",
              BindingFlags.InvokeMethod,
              null,
              ptInstance,
              new object[0]);
   }
}

Remarks

The string must have already been defined.

EmitWriteLine(FieldInfo)

Source:

ILGenerator.cs

Emits the Microsoft intermediate language (MSIL) necessary to call WriteLine with the given field.

C#

public virtual void EmitWriteLine(System.Reflection.FieldInfo fld);

Parameters

fld

FieldInfo

The field whose value is to be written to the console.

Exceptions

ArgumentException

There is no overload of the WriteLine method that accepts the type of the specified field.

ArgumentNullException

fld is null.

NotSupportedException

The type of the field is TypeBuilder or EnumBuilder, which are not supported.

Examples

The following code sample demonstrates the use of the EmitWriteLine method to write a string to the console in a dynamic method.

C#

using System;
using System.Threading;
using System.Reflection;
using System.Reflection.Emit;

class EmitWriteLineDemo {

   public static Type CreateDynamicType() {
       Type[] ctorParams = new Type[] {typeof(int),
                   typeof(int)};
    
       AppDomain myDomain = Thread.GetDomain();
       AssemblyName myAsmName = new AssemblyName();
       myAsmName.Name = "MyDynamicAssembly";

       AssemblyBuilder myAsmBuilder = myDomain.DefineDynamicAssembly(
                      myAsmName,
                      AssemblyBuilderAccess.Run);

       ModuleBuilder pointModule = myAsmBuilder.DefineDynamicModule("PointModule",
                                    "Point.dll");

       TypeBuilder pointTypeBld = pointModule.DefineType("Point",
                                  TypeAttributes.Public);

       FieldBuilder xField = pointTypeBld.DefineField("x", typeof(int),
                                                      FieldAttributes.Public);
       FieldBuilder yField = pointTypeBld.DefineField("y", typeof(int),
                                                      FieldAttributes.Public);

       Type objType = Type.GetType("System.Object");
       ConstructorInfo objCtor = objType.GetConstructor(new Type[0]);

       ConstructorBuilder pointCtor = pointTypeBld.DefineConstructor(
                                   MethodAttributes.Public,
                                   CallingConventions.Standard,
                                   ctorParams);
       ILGenerator ctorIL = pointCtor.GetILGenerator();

       // First, you build the constructor.
       ctorIL.Emit(OpCodes.Ldarg_0);
       ctorIL.Emit(OpCodes.Call, objCtor);
       ctorIL.Emit(OpCodes.Ldarg_0);
       ctorIL.Emit(OpCodes.Ldarg_1);
       ctorIL.Emit(OpCodes.Stfld, xField);
       ctorIL.Emit(OpCodes.Ldarg_0);
       ctorIL.Emit(OpCodes.Ldarg_2);
       ctorIL.Emit(OpCodes.Stfld, yField);
       ctorIL.Emit(OpCodes.Ret);

       //  Now, you'll build a method to output some information on the
       // inside your dynamic class. This method will have the following
       // definition in C#:
    //  public void WritePoint()

       MethodBuilder writeStrMthd = pointTypeBld.DefineMethod(
                                     "WritePoint",
                             MethodAttributes.Public,
                                             typeof(void),
                                             null);

       ILGenerator writeStrIL = writeStrMthd.GetILGenerator();

       // The below ILGenerator created demonstrates a few ways to create
       // string output through STDIN.

       // ILGenerator.EmitWriteLine(string) will generate a ldstr and a
       // call to WriteLine for you.

       writeStrIL.EmitWriteLine("The value of this current instance is:");

       // Here, you will do the hard work yourself. First, you need to create
       // the string we will be passing and obtain the correct WriteLine overload
       // for said string. In the below case, you are substituting in two values,
       // so the chosen overload is Console.WriteLine(string, object, object).

       String inStr = "({0}, {1})";
       Type[] wlParams = new Type[] {typeof(string),
                     typeof(object),
                     typeof(object)};

       // We need the MethodInfo to pass into EmitCall later.

       MethodInfo writeLineMI = typeof(Console).GetMethod(
                            "WriteLine",
                        wlParams);

       // Push the string with the substitutions onto the stack.
       // This is the first argument for WriteLine - the string one.

       writeStrIL.Emit(OpCodes.Ldstr, inStr);

       // Since the second argument is an object, and it corresponds to
       // to the substitution for the value of our integer field, you
       // need to box that field to an object. First, push a reference
       // to the current instance, and then push the value stored in
       // field 'x'. We need the reference to the current instance (stored
       // in local argument index 0) so Ldfld can load from the correct
       // instance (this one).

       writeStrIL.Emit(OpCodes.Ldarg_0);
       writeStrIL.Emit(OpCodes.Ldfld, xField);

       // Now, we execute the box opcode, which pops the value of field 'x',
       // returning a reference to the integer value boxed as an object.

       writeStrIL.Emit(OpCodes.Box, typeof(int));

       // Atop the stack, you'll find our string inStr, followed by a reference
       // to the boxed value of 'x'. Now, you need to likewise box field 'y'.

       writeStrIL.Emit(OpCodes.Ldarg_0);
       writeStrIL.Emit(OpCodes.Ldfld, yField);
       writeStrIL.Emit(OpCodes.Box, typeof(int));

       // Now, you have all of the arguments for your call to
       // Console.WriteLine(string, object, object) atop the stack:
       // the string InStr, a reference to the boxed value of 'x', and
       // a reference to the boxed value of 'y'.

       // Call Console.WriteLine(string, object, object) with EmitCall.

       writeStrIL.EmitCall(OpCodes.Call, writeLineMI, null);

       // Lastly, EmitWriteLine can also output the value of a field
       // using the overload EmitWriteLine(FieldInfo).

       writeStrIL.EmitWriteLine("The value of 'x' is:");
       writeStrIL.EmitWriteLine(xField);
       writeStrIL.EmitWriteLine("The value of 'y' is:");
       writeStrIL.EmitWriteLine(yField);

       // Since we return no value (void), the ret opcode will not
       // return the top stack value.

       writeStrIL.Emit(OpCodes.Ret);

       return pointTypeBld.CreateType();
   }

   public static void Main() {

      object[] ctorParams = new object[2];

      Console.Write("Enter a integer value for X: ");
      string myX = Console.ReadLine();
      Console.Write("Enter a integer value for Y: ");
      string myY = Console.ReadLine();

      Console.WriteLine("---");

      ctorParams[0] = Convert.ToInt32(myX);
      ctorParams[1] = Convert.ToInt32(myY);

      Type ptType = CreateDynamicType();

      object ptInstance = Activator.CreateInstance(ptType, ctorParams);
      ptType.InvokeMember("WritePoint",
              BindingFlags.InvokeMethod,
              null,
              ptInstance,
              new object[0]);
   }
}

Remarks

The type of fld must match the parameter type of an overload of the Console.WriteLine method.

EmitWriteLine(LocalBuilder)

Source:

ILGenerator.cs

Emits the Microsoft intermediate language (MSIL) necessary to call WriteLine with the given local variable.

C#

public virtual void EmitWriteLine(System.Reflection.Emit.LocalBuilder localBuilder);

Parameters

localBuilder

LocalBuilder

The local variable whose value is to be written to the console.

Exceptions

ArgumentException

The type of localBuilder is TypeBuilder or EnumBuilder, which are not supported.

-or-

There is no overload of WriteLine that accepts the type of localBuilder.

ArgumentNullException

localBuilder is null.

Examples

The code sample below demonstrates the contextual usage of the EmitWriteLine method to write a string to the console in a dynamic method.

C#

using System;
using System.Threading;
using System.Reflection;
using System.Reflection.Emit;

class EmitWriteLineDemo {

   public static Type CreateDynamicType() {
       Type[] ctorParams = new Type[] {typeof(int),
                   typeof(int)};
    
       AppDomain myDomain = Thread.GetDomain();
       AssemblyName myAsmName = new AssemblyName();
       myAsmName.Name = "MyDynamicAssembly";

       AssemblyBuilder myAsmBuilder = myDomain.DefineDynamicAssembly(
                      myAsmName,
                      AssemblyBuilderAccess.Run);

       ModuleBuilder pointModule = myAsmBuilder.DefineDynamicModule("PointModule",
                                    "Point.dll");

       TypeBuilder pointTypeBld = pointModule.DefineType("Point",
                                  TypeAttributes.Public);

       FieldBuilder xField = pointTypeBld.DefineField("x", typeof(int),
                                                      FieldAttributes.Public);
       FieldBuilder yField = pointTypeBld.DefineField("y", typeof(int),
                                                      FieldAttributes.Public);

       Type objType = Type.GetType("System.Object");
       ConstructorInfo objCtor = objType.GetConstructor(new Type[0]);

       ConstructorBuilder pointCtor = pointTypeBld.DefineConstructor(
                                   MethodAttributes.Public,
                                   CallingConventions.Standard,
                                   ctorParams);
       ILGenerator ctorIL = pointCtor.GetILGenerator();

       // First, you build the constructor.
       ctorIL.Emit(OpCodes.Ldarg_0);
       ctorIL.Emit(OpCodes.Call, objCtor);
       ctorIL.Emit(OpCodes.Ldarg_0);
       ctorIL.Emit(OpCodes.Ldarg_1);
       ctorIL.Emit(OpCodes.Stfld, xField);
       ctorIL.Emit(OpCodes.Ldarg_0);
       ctorIL.Emit(OpCodes.Ldarg_2);
       ctorIL.Emit(OpCodes.Stfld, yField);
       ctorIL.Emit(OpCodes.Ret);

       //  Now, you'll build a method to output some information on the
       // inside your dynamic class. This method will have the following
       // definition in C#:
    //  public void WritePoint()

       MethodBuilder writeStrMthd = pointTypeBld.DefineMethod(
                                     "WritePoint",
                             MethodAttributes.Public,
                                             typeof(void),
                                             null);

       ILGenerator writeStrIL = writeStrMthd.GetILGenerator();

       // The below ILGenerator created demonstrates a few ways to create
       // string output through STDIN.

       // ILGenerator.EmitWriteLine(string) will generate a ldstr and a
       // call to WriteLine for you.

       writeStrIL.EmitWriteLine("The value of this current instance is:");

       // Here, you will do the hard work yourself. First, you need to create
       // the string we will be passing and obtain the correct WriteLine overload
       // for said string. In the below case, you are substituting in two values,
       // so the chosen overload is Console.WriteLine(string, object, object).

       String inStr = "({0}, {1})";
       Type[] wlParams = new Type[] {typeof(string),
                     typeof(object),
                     typeof(object)};

       // We need the MethodInfo to pass into EmitCall later.

       MethodInfo writeLineMI = typeof(Console).GetMethod(
                            "WriteLine",
                        wlParams);

       // Push the string with the substitutions onto the stack.
       // This is the first argument for WriteLine - the string one.

       writeStrIL.Emit(OpCodes.Ldstr, inStr);

       // Since the second argument is an object, and it corresponds to
       // to the substitution for the value of our integer field, you
       // need to box that field to an object. First, push a reference
       // to the current instance, and then push the value stored in
       // field 'x'. We need the reference to the current instance (stored
       // in local argument index 0) so Ldfld can load from the correct
       // instance (this one).

       writeStrIL.Emit(OpCodes.Ldarg_0);
       writeStrIL.Emit(OpCodes.Ldfld, xField);

       // Now, we execute the box opcode, which pops the value of field 'x',
       // returning a reference to the integer value boxed as an object.

       writeStrIL.Emit(OpCodes.Box, typeof(int));

       // Atop the stack, you'll find our string inStr, followed by a reference
       // to the boxed value of 'x'. Now, you need to likewise box field 'y'.

       writeStrIL.Emit(OpCodes.Ldarg_0);
       writeStrIL.Emit(OpCodes.Ldfld, yField);
       writeStrIL.Emit(OpCodes.Box, typeof(int));

       // Now, you have all of the arguments for your call to
       // Console.WriteLine(string, object, object) atop the stack:
       // the string InStr, a reference to the boxed value of 'x', and
       // a reference to the boxed value of 'y'.

       // Call Console.WriteLine(string, object, object) with EmitCall.

       writeStrIL.EmitCall(OpCodes.Call, writeLineMI, null);

       // Lastly, EmitWriteLine can also output the value of a field
       // using the overload EmitWriteLine(FieldInfo).

       writeStrIL.EmitWriteLine("The value of 'x' is:");
       writeStrIL.EmitWriteLine(xField);
       writeStrIL.EmitWriteLine("The value of 'y' is:");
       writeStrIL.EmitWriteLine(yField);

       // Since we return no value (void), the ret opcode will not
       // return the top stack value.

       writeStrIL.Emit(OpCodes.Ret);

       return pointTypeBld.CreateType();
   }

   public static void Main() {

      object[] ctorParams = new object[2];

      Console.Write("Enter a integer value for X: ");
      string myX = Console.ReadLine();
      Console.Write("Enter a integer value for Y: ");
      string myY = Console.ReadLine();

      Console.WriteLine("---");

      ctorParams[0] = Convert.ToInt32(myX);
      ctorParams[1] = Convert.ToInt32(myY);

      Type ptType = CreateDynamicType();

      object ptInstance = Activator.CreateInstance(ptType, ctorParams);
      ptType.InvokeMember("WritePoint",
              BindingFlags.InvokeMethod,
              null,
              ptInstance,
              new object[0]);
   }
}

Remarks

The type of localBuilder must match the parameter type of an overload of the Console.WriteLine method.