protected override Expression VisitMember(MemberExpression node)
{
if (node.Expression is ParameterExpression)
{
//访问到了根节点了
if (_properties.Count <= 0)
{
_columnInfos.Add(node.Member.Name, new KeyValuePair <string, string>(_masterTableName, node.Member.Name));
}
else
{
Type type = node.Type;
if (type.IsGenericType)
{
type = Nullable.GetUnderlyingType(type);
}
if (!(type.FullName == "System.DateTime" && type.Assembly.GlobalAssemblyCache))
{
throw new ArgumentException("Select子句中多个属性访问的表达式时，若属性名为Date，则只能支持访问DateTime类型的实体，例如x.Time.Date");
}
NeedWrapSelect = true;
_columnInfos.Add(node.Member.Name, new KeyValuePair <string, string>(_masterTableName, node.Member.Name));
_columnMethods.Add(new KeyValuePair <string, string>(_masterTableName, node.Member.Name), "CONVERT(NVARCHAR(20),{0},101)");
if (!_tableInfos.ContainsKey(_masterTableName))
{
_tableInfos.Add(_masterTableName, ExpressionUtil.GenerateRandomTableAlias());
}
_properties.Clear();
}
}
else
{
//不是根节点，取出Member属性用于计算值
PropertyInfo propertyInfo = (PropertyInfo)node.Member;
if (propertyInfo.Name == "Value")
{
propertyInfo = (PropertyInfo)((MemberExpression)node.Expression).Member;
//跳过可空类型
if (!propertyInfo.PropertyType.IsGenericType)
{
throw new ArgumentException("在Select子句中，若使用了多个属性访问的表达式并且属性名为Value，则该表达式只允许为访问Nullable<T>的表达式，例如如果实体的Time为DateTime?，则可以写为x.Time.Value");
}
else
{
return(base.VisitMember(node));
}
}
NeedWrapSelect = true;
_properties.Push(propertyInfo);
}
return(base.VisitMember(node));
}
protected override Expression VisitNew(NewExpression node)
{
//此处一般是在Select方法中new了匿名对象，例如users.Select(x=>new {x.Id})
foreach (System.Reflection.MemberInfo memberInfo in node.Members)
{
//检查当前成员的类型是否是实体类型，例如x=>new {x.User.Book.Id}
//这种情况一般是外键访问，需要考虑与主表之间的关系
if (ExpressionUtil.IsEntityMember(memberInfo))
{
//当前成员的类型是一个实体类型，需要考虑与主表的关系
var type = ExpressionUtil.GetMemberType(memberInfo);
var entityInfo = _entityManager.GetEntity(type);
var parentExpression = FindArgument(node.Arguments, memberInfo);
if (parentExpression is ParameterExpression)
{
//该成员由参数直接调用，可直接考虑与主表的关系
}
string tableName = entityInfo.TableName;
//if (string.IsNullOrWhiteSpace(tableName))
//{
// throw new Exception("Select子句中选择的类型没有标TableAttribute特性或者特性中指定了空表名");
//}
var pis = entityInfo.Properties;
//_alias.AddRange(pis.Select(x => x.Name));
foreach (var propertyInfo in pis)
{
_columnInfos.Add(propertyInfo.Name, new KeyValuePair <string, string>(tableName, propertyInfo.Name));
}
if (!_tableInfos.ContainsKey(tableName))
{
_tableInfos.Add(tableName, ExpressionUtil.GenerateRandomTableAlias());
}
}
else
{
_columnInfos.Add(memberInfo.Name, new KeyValuePair <string, string>(_masterTableName, memberInfo.Name));
}
}
return(node);
}