/// <summary>Generates state transfer expressions to copy a complex type</summary>
/// <param name="clonedType">Complex type that will be cloned</param>
/// <param name="original">Variable expression for the original instance</param>
/// <param name="clone">Variable expression for the cloned instance</param>
/// <param name="variables">Receives variables used by the transfer expressions</param>
/// <param name="transferExpressions">Receives the generated transfer expressions</param>
private static void generateFieldBasedComplexTypeTransferExpressions(
Type clonedType, // Actual, concrete type (not declared type)
Expression original, // Expected to be an object
Expression clone, // As actual, concrete type
IList <ParameterExpression> variables,
ICollection <Expression> transferExpressions
)
{
// Enumerate all of the type's fields and generate transfer expressions for each
var fieldInfos = ClonerHelpers.GetFieldInfosIncludingBaseClasses(
clonedType, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance
);
for (var index = 0; index < fieldInfos.Length; ++index)
{
var fieldInfo = fieldInfos[index];
var fieldType = fieldInfo.FieldType;
if (fieldType.IsPrimitive || (fieldType == typeof(string)))
{
// Primitive types and strings can be transferred by simple assignment
transferExpressions.Add(
Expression.Assign(
Expression.Field(clone, fieldInfo),
Expression.Field(original, fieldInfo)
)
);
}
else if (fieldType.IsValueType)
{
// A nested value type is part of the parent and will have its fields directly
// assigned without boxing, new instance creation or anything like that.
generateFieldBasedComplexTypeTransferExpressions(
fieldType,
Expression.Field(original, fieldInfo),
Expression.Field(clone, fieldInfo),
variables,
transferExpressions
);
}
else
{
generateFieldBasedReferenceTypeTransferExpressions(
original, clone, transferExpressions, fieldInfo, fieldType
);
}
}
}
/// <summary>Compiles a method that creates a shallow clone of an object</summary>
/// <param name="clonedType">Type for which a clone method will be created</param>
/// <returns>A method that clones an object of the provided type</returns>
private static Func <object, object> createShallowFieldBasedCloner(Type clonedType)
{
var original = Expression.Parameter(typeof(object), "original");
var transferExpressions = new List <Expression>();
var variables = new List <ParameterExpression>();
if (clonedType.IsPrimitive || clonedType.IsValueType || (clonedType == typeof(string)))
{
// Primitives and strings are copied on direct assignment
transferExpressions.Add(original);
}
else if (clonedType.IsArray)
{
transferExpressions.Add(
generateFieldBasedPrimitiveArrayTransferExpressions(
clonedType, original, variables, transferExpressions
)
);
}
else
{
// We need a variable to hold the clone because due to the assignments it
// won't be last in the block when we're finished
var clone = Expression.Variable(clonedType);
variables.Add(clone);
// To access the fields of the original type, we need it to be of the actual
// type instead of an object, so perform a downcast
var typedOriginal = Expression.Variable(clonedType);
variables.Add(typedOriginal);
transferExpressions.Add(
Expression.Assign(typedOriginal, Expression.Convert(original, clonedType))
);
// Give it a new instance of the type being cloned
var getUninitializedObjectMethodInfo = typeof(FormatterServices).GetMethod(
"GetUninitializedObject", BindingFlags.Static | BindingFlags.Public
);
transferExpressions.Add(
Expression.Assign(
clone,
Expression.Convert(
Expression.Call(
getUninitializedObjectMethodInfo, Expression.Constant(clonedType)
),
clonedType
)
)
);
// Enumerate all of the type's fields and generate transfer expressions for each
var fieldInfos = ClonerHelpers.GetFieldInfosIncludingBaseClasses(
clonedType, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance
);
transferExpressions.AddRange(
fieldInfos.Select(fieldInfo => Expression.Assign(Expression.Field(clone, fieldInfo), Expression.Field(typedOriginal, fieldInfo))));
// Make sure the clone is the last thing in the block to set the return value
transferExpressions.Add(clone);
}
// Turn all transfer expressions into a single block if necessary
Expression resultExpression;
if ((transferExpressions.Count == 1) && (variables.Count == 0))
{
resultExpression = transferExpressions[0];
}
else
{
resultExpression = Expression.Block(variables, transferExpressions);
}
// Value types require manual boxing
if (clonedType.IsValueType)
{
resultExpression = Expression.Convert(resultExpression, typeof(object));
}
return(Expression.Lambda <Func <object, object> >(resultExpression, original).Compile());
}
