public virtual IQueryState Accept(AggregateQueryExpression exp)
{
List <DbExpression> dbArguments = new List <DbExpression>(exp.Arguments.Count);
foreach (Expression argument in exp.Arguments)
{
var arg = (LambdaExpression)argument;
ScopeParameterDictionary scopeParameters = this._queryModel.ScopeParameters.Clone(arg.Parameters[0], this._queryModel.ResultModel);
var dbArgument = GeneralExpressionParser.Parse(arg, scopeParameters, this._queryModel.ScopeTables);
dbArguments.Add(dbArgument);
}
DbAggregateExpression dbAggregateExp = new DbAggregateExpression(exp.ElementType, exp.Method, dbArguments);
PrimitiveObjectModel resultModel = new PrimitiveObjectModel(exp.ElementType, dbAggregateExp);
QueryModel queryModel = new QueryModel(this._queryModel.ScopeParameters, this._queryModel.ScopeTables, this._queryModel.IgnoreFilters);
queryModel.ResultModel = resultModel;
queryModel.FromTable = this._queryModel.FromTable;
queryModel.AppendCondition(this._queryModel.Condition);
AggregateQueryState state = new AggregateQueryState(queryModel);
return(state);
}
protected override DbExpression VisitParameter(ParameterExpression exp)
{
//只支持 MappingFieldExpression 类型，即类似 q.Select(a=> a.Id).Where(a=> a > 0) 这种情况，也就是 ParameterExpression.Type 为基本映射类型。
if (MappingTypeSystem.IsMappingType(exp.Type))
{
IObjectModel model = this.FindModel(exp);
PrimitiveObjectModel resultModel = (PrimitiveObjectModel)model;
return(resultModel.Expression);
}
else
{
throw new NotSupportedException(exp.ToString());
}
}