/// <summary>
/// 访问字段或者属性表达式
/// </summary>
/// <param name="node">字段或者成员表达式</param>
/// <returns></returns>
protected override Expression VisitMember(MemberExpression node)
{
// 1.<>h__TransparentIdentifier3.b.Client.ClientName
// 2.<>h__TransparentIdentifier3.b.Client.ClientName.Length
// 3.<>h__TransparentIdentifier3.b.Client.Address.AddressName
// 4.<>h__TransparentIdentifier3.b.ClientName
// <>h__TransparentIdentifier2.<>h__TransparentIdentifier3.b.ClientName
// <>h__TransparentIdentifier2.<>h__TransparentIdentifier3.b.Client.ClientName
// <>h__TransparentIdentifier2.<>h__TransparentIdentifier3.b.Client.Address.AddressName
// 5.b.ClientName
if (node == null)
{
return(node);
}
// => a.ActiveDate == DateTime.Now => a.State == (byte)state
if (node.CanEvaluate())
{
return(this.VisitConstant(node.Evaluate()));
}
// => DateTime.Now
if (node.Type == typeof(DateTime) && node.Expression == null)
{
return(this.VisitMethodCall(node, MethodCallType.MemberMember));
}
// => a.Nullable.Value
bool isNullable = node.Expression.Type.IsGenericType && node.Member.Name == "Value" && node.Expression.Type.GetGenericTypeDefinition() == typeof(Nullable <>);
if (isNullable)
{
this.Visit(node.Expression);
return(node);
}
// 记录访问成员栈
_visitedStack.Add(node);
// => a.Name.Length
if (TypeUtils.IsPrimitiveType(node.Expression.Type))
{
return(this.VisitMethodCall(node, MethodCallType.MemberMember));
}
// => <>h__3.b.ClientName
if (!node.Expression.Visitable())
{
_builder.AppendMember(_ag, node);
return(node);
}
// => a.Accounts[0].Markets[0].MarketId
// => b.Client.Address.AddressName
Expression objExpression = node.Expression;
bool isMethodCall = objExpression != null && objExpression.NodeType == ExpressionType.Call;
if (isMethodCall)
{
MethodCallExpression methodExpression = objExpression as MethodCallExpression;
bool isIndex = methodExpression.IsCollectionIndex();
if (isIndex)
{
objExpression = methodExpression.Object;
}
}
// => b.Client.Address.AddressName
this.VisitNavMember(objExpression, TypeUtils.GetFieldName(node.Member, node.Expression.Type));
return(node);
}
/// <summary>
/// 判断表达式链是否能通过动态计算，计算出它的值
/// </summary>
public static bool CanEvaluate(this Expression node)
{
// => 5
// => a.ActiveDate == DateTime.Now
// => a.State == (byte)state
// => a.Accounts[0].Markets[0].MarketId
if (node == null)
{
return(false);
}
if (node.NodeType == ExpressionType.Constant)
{
return(true);
}
if (node.NodeType == ExpressionType.ArrayIndex)
{
return(true);
}
if (node.NodeType == ExpressionType.Call)
{
// List<int>{0}[]
// => a.Accounts[0].Markets[0].MarketId
MethodCallExpression methodExpression = node as MethodCallExpression;
bool isIndex = methodExpression.IsCollectionIndex();
if (isIndex)
{
node = methodExpression.Object;
}
}
if (node.NodeType == ExpressionType.ListInit)
{
return(true);
}
if (node.NodeType == ExpressionType.NewArrayInit)
{
return(true);
}
if (node.NodeType == ExpressionType.NewArrayBounds)
{
return(true);
}
if (node.NodeType != ExpressionType.MemberAccess)
{
return(false);
}
var memberExpression = node as MemberExpression;
if (memberExpression == null)
{
return(false);
}
if (memberExpression.Expression == null)
{
// 排除 DateTime 的几个常量
bool isDateTime = memberExpression.Type == typeof(DateTime) &&
(memberExpression.Member.Name == "Now" || memberExpression.Member.Name == "UtcNow" || memberExpression.Member.Name == "Today");
return(!isDateTime);
}
if (memberExpression.Expression.NodeType == ExpressionType.Constant)
{
return(true);
}
return(memberExpression.Expression.CanEvaluate());
}
