// 记录选中字段
private void AddSelectedColumn(MemberInfo m, Type reflectedType)
{
string memberName = m.Name;
var srcDbExpressionType = _builder.TranslateContext.CurrentExpressionType;
var srcIsOutermost = _builder.TranslateContext.CurrentIsOutermost;
if (!(srcDbExpressionType == DbExpressionType.Select && srcIsOutermost == true))
{
// 非外层字段，SELECT xx As name 的 name 使用数据库原生字段
memberName = TypeUtils.GetFieldName(m, reflectedType);
}
// 选择字段
string newName = _selectedColumns.Add(memberName);
_builder.AppendAs(newName);
_builder.Append(",");
_builder.AppendNewLine();
}
/// <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>
/// 访问 Lambda 表达式，如 p=>p p=>p.t p=>p.Id
/// </summary>
/// <typeparam name="T">返回类型</typeparam>
/// <param name="node">Lambda 表达式</param>
/// <returns></returns>
protected override Expression VisitLambda <T>(Expression <T> node)
{
LambdaExpression lambda = node as LambdaExpression;
if (lambda.Body.NodeType == ExpressionType.Parameter)
{
// 例： a=> a
Type type = lambda.Body.Type;
string alias = _ag.GetTableAlias(lambda);
this.VisitAllMember(type, alias);
return(node);
}
else if (lambda.Body.CanEvaluate())
{
// 例：a=>1
base.Visit(lambda.Body.Evaluate());
// 选择字段
string newName = _selectedColumns.Add(AppConst.CONSTANT_COLUMN_NAME);
// 添加字段别名
_builder.AppendAs(newName);
return(node);
}
else if (lambda.Body.NodeType == ExpressionType.MemberAccess)
{
// 例： t=> t.a
// => SELECT a.ClientId
Type type = lambda.Body.Type;
if (!TypeUtils.IsPrimitiveType(type))
{
return(this.VisitAllMember(type, _ag.GetTableAlias(lambda.Body), node));
}
else
{
var newNode = this.VisitWithoutStack(_ => base.VisitLambda(node));
var memberExpression = lambda.Body as MemberExpression;
string memberName = memberExpression.Member.Name;
var srcDbExpressionType = _builder.TranslateContext.CurrentExpressionType;
var srcIsOutermost = _builder.TranslateContext.CurrentIsOutermost;
if (!(srcDbExpressionType != null && srcDbExpressionType == DbExpressionType.Select && srcIsOutermost != null && srcIsOutermost.Value))
{
// 非外层字段，SELECT xx As name 的 name 使用数据库原生字段
memberName = TypeUtils.GetFieldName(memberExpression.Member, memberExpression.Expression.Type);
}
string newName = _selectedColumns.Add(memberName);
return(newNode);
}
}
else
{
// 例：a => a.DemoCode，选择字段仅选一个基元类型字段。
// 结果可能返回一个比如字符串类型列表
var newNode = base.VisitLambda(node);
if (_selectedColumns.Count == 0)
{
// 选择字段
string newName = _selectedColumns.Add(AppConst.CONSTANT_COLUMN_NAME);
// 添加字段别名
_builder.AppendAs(newName);
}
return(newNode);
}
}
