public static void CreateMemberInitExpression()
{
System.Linq.Expressions.NewExpression newAnimal =
System.Linq.Expressions.Expression.New(typeof(Animal));
System.Reflection.MemberInfo speciesMember =
typeof(Animal).GetMember("Species")[0];
System.Reflection.MemberInfo ageMember =
typeof(Animal).GetMember("Age")[0];
// Create a MemberBinding object for each member
// that you want to initialize.
System.Linq.Expressions.MemberBinding speciesMemberBinding =
System.Linq.Expressions.Expression.Bind(
speciesMember,
System.Linq.Expressions.Expression.Constant("horse"));
System.Linq.Expressions.MemberBinding ageMemberBinding =
System.Linq.Expressions.Expression.Bind(
ageMember,
System.Linq.Expressions.Expression.Constant(12));
// Create a MemberInitExpression that represents initializing
// two members of the 'Animal' class.
System.Linq.Expressions.MemberInitExpression memberInitExpression =
System.Linq.Expressions.Expression.MemberInit(
newAnimal,
speciesMemberBinding,
ageMemberBinding);
//// Create a MemberInitExpression that represents initializing
//// two members of the 'Animal' class.
//System.Linq.Expressions.MemberInitExpression memberInitExpression =
// System.Linq.Expressions.Expression.MemberInit(
// newAnimal,
// speciesMemberBinding);
Console.WriteLine(memberInitExpression.ToString());
var expression = Expression.Lambda <Func <Dog, Animal> >(memberInitExpression);
var compile = expression.Compile();
var dog = new Dog()
{
Species = "DOG"
};
var test = compile(dog);
Console.WriteLine(test.ToJson());
// This code produces the following output:
//
// new Animal() {Species = "horse", Age = 12}
}
internal override Expression VisitMemberInit(MemberInitExpression init)
{
if (!ClientTypeUtil.TypeOrElementTypeIsEntity(init.Type))
{
throw new NotSupportedException(System.Data.Services.Client.Strings.ALinq_ExpressionNotSupportedInProjectionToEntity(this.type, init.ToString()));
}
ProjectionAnalyzer.Analyze(init, this.box, this.context);
return init;
}
internal override Expression VisitMemberInit(MemberInitExpression init)
{
if (!ClientTypeUtil.TypeOrElementTypeIsEntity(init.Type))
{
// MemberInit to a complex type is not supported on entity types.
throw new NotSupportedException(Strings.ALinq_ExpressionNotSupportedInProjectionToEntity(this.type, init.ToString()));
}
ProjectionAnalyzer.Analyze(init, this.builder, this.context);
return init;
}
private void VisitMemberInit(MemberInitExpression node)
{
foreach (var memberBinding in node.Bindings)
{
var memberAssignment = memberBinding as MemberAssignment;
if (memberAssignment != null)
{
_mappings.Add(new ProjectionMemberMapping
{
Expression = memberAssignment.Expression,
Member = memberAssignment.Member
});
}
else
{
var message = string.Format("Only member assignments are supported in a new expression in $project and $group, but found {0}.",
node.ToString());
throw new NotSupportedException(message);
}
}
VisitNew(node.NewExpression);
}
