public EnumerationData(Type itemType)
{
EnumerableType = typeof(IEnumerable <>).MakeGenericType(itemType);
EnumeratorType = typeof(IEnumerator <>).MakeGenericType(itemType);
GetEnumerator = EnumerableType.GetMethod("GetEnumerator", new Type[0]);
Current = EnumeratorType.GetProperty("Current");
}
private void EmitILForEachView(ILGenerator il, Action forEachAction)
{
Debug.Assert(il != null);
Debug.Assert(forEachAction != null);
// Declare the locals we need
var viewLocal = il.DeclareLocal(_viewType);
var enumeratorLocal = il.DeclareLocal(EnumerableType);
var enumeratorContinueLocal = il.DeclareLocal(typeof(bool));
// Load the view instance on to the evaluation stack
il.Emit(OpCodes.Ldarg, viewLocal.LocalIndex);
// Call CompositeView<IViewType>.get_Views
var getViews = GetCompositeViewViewsPropertyGetter();
il.EmitCall(OpCodes.Call, getViews, null);
// Call IEnumerable<>.GetEnumerator
var getViewsEnumerator = EnumerableType
.GetMethod(
"GetEnumerator",
BindingFlags.Instance | BindingFlags.DeclaredOnly | BindingFlags.Public);
il.EmitCall(OpCodes.Callvirt, getViewsEnumerator, null);
// Push the enumerator from the evaluation stack to the local variable
il.Emit(OpCodes.Stloc, enumeratorLocal.LocalIndex);
// Start a new exception block so that we can reliably dispose
// the enumerator
il.BeginExceptionBlock();
// Define some of the labels we need
var moveNextLabel = il.DefineLabel();
var continueLabel = il.DefineLabel();
var endFinallyLabel = il.DefineLabel();
var exitLabel = il.DefineLabel();
// Skip straight ahead to moveNextLabel
il.Emit(OpCodes.Br_S, moveNextLabel);
// Mark this point with with continueLabel
il.MarkLabel(continueLabel);
// Push the enumerator on to the evaluation stack
il.Emit(OpCodes.Ldloc, enumeratorLocal);
// Call IEnumerator<>.get_Current on the enumerator
var getCurrent = EnumeratorType.GetProperty("Current")?.GetGetMethod();
il.EmitCall(OpCodes.Callvirt, getCurrent, null);
// Store the output from IEnumerator<>.get_Current into a local
il.Emit(OpCodes.Stloc, viewLocal);
// Push the view local back onto the evaluation stack
il.Emit(OpCodes.Ldloc, viewLocal);
// Push the incoming set value onto the evaluation stack
il.Emit(OpCodes.Ldarg, 1);
// Let the calling method inject some IL here
forEachAction();
// Mark this point with the moveNextLabel
il.MarkLabel(moveNextLabel);
// Push the enumerator local back onto the evaluation stack
il.Emit(OpCodes.Ldloc, enumeratorLocal);
// Call IEnumerator.MoveNext on the enumerator
var moveNext = typeof(IEnumerator).GetMethod("MoveNext");
il.EmitCall(OpCodes.Callvirt, moveNext, null);
// Push the result of MoveNext from the evaluation stack to the local variable
il.Emit(OpCodes.Stloc, enumeratorContinueLocal.LocalIndex);
// Pull the result of MoveNext from the evaluation stack back onto the evaluation stack
il.Emit(OpCodes.Ldloc, enumeratorContinueLocal.LocalIndex);
// If MoveNext returned true, jump back to the continue label
il.Emit(OpCodes.Brtrue_S, continueLabel);
// Jump out of the try block
il.Emit(OpCodes.Leave_S, exitLabel);
// Start the finally block
il.BeginFinallyBlock();
// Push the enumerator onto the evaluation stack, then compare against null
il.Emit(OpCodes.Ldloc, enumeratorLocal);
il.Emit(OpCodes.Ldnull);
il.Emit(OpCodes.Ceq);
// Pop the comparison result into our local
il.Emit(OpCodes.Stloc, enumeratorContinueLocal);
// If the comparison result was true, jump to the end of the finally block
il.Emit(OpCodes.Ldloc, enumeratorContinueLocal);
il.Emit(OpCodes.Brtrue_S, endFinallyLabel);
// Push the enumerator onto the evaluation stack
il.Emit(OpCodes.Ldloc, enumeratorLocal);
// Call IDisposable.Dispose
var dispose = typeof(IDisposable).GetMethod("Dispose");
il.Emit(OpCodes.Callvirt, dispose);
// Mark this point as exit point for our finally block
il.MarkLabel(endFinallyLabel);
// Close the try block
il.EndExceptionBlock();
// Mark this point as our exit point (used to get out of the try block)
il.MarkLabel(exitLabel);
}
