如何使用动态构建的Lambda表达式创建和填充动态对象 [英] How do I create and populate a dynamic object using a dynamically built lambda expression
问题描述
我正在尝试从仅在运行时已知的数据集中创建和填充动态对象.在下面的代码中,我从数据集中创建了IEnumerable结果,其中包含一些已知字段(ID,主数据,DisplayOrder,IsActive)和一个在设计时不知道的用户定义字段(电话号码),因此必须动态构建.下面的代码有效,但这仅是因为我已经对动态字段电话号码"进行了硬编码.如何动态构建Lambda表达式以处理仅在运行时才知道的字段.我想要
I'm trying to create and populate a dynamic object from a dataset that is only known at run time. In the code below, I create my IEnumerable results from my dataset with some known fields (ID, Primary Data, DisplayOrder, IsActive) and one user-define field (Phone Number) which I won't know at design time, and therefore must be built dynamically. The code below works, but only because I've hard-coded the dynamic field Phone Number. How do I build the Lambda expression dynamically to handle those fields only known at runtime. I want the equivalent of
string fieldName = 'PhoneNumber = ';
string fieldSource = 'pd.tbList_DataText';
string expression = 'pd=>new { ID = pd.ID, PrimaryData=pd.PrimaryData';
expression += fieldName;
expression += FieldSource;
expression += '.Where(ld => ld.DataRowID == pd.ID && ld.ListColumnID == 1).Select(ld => ld.DataField).DefaultIfEmpty("").First()})';
var results = primaryData.Select(expression);
那我该怎么做呢?谢谢
// Get base Data
IEnumerable<tbList_Data> primaryData = await _tbList_DataRepository.GetAsync(ld => ld.ListID == listId && (ld.IsActive == includeInactive ? ld.IsActive : true));
// Get Final Results
var results = primaryData.Select(pd => new {
Id = pd.ID,
PrimaryData = pd.PrimaryData,
PhoneNumber = pd.tbList_DataText.Where(ld => ld.DataRowID == pd.ID && ld.ListColumnID == 1).Select(ld => ld.DataField).DefaultIfEmpty("").First()
});
推荐答案
我看到几个选项.
1)元组
var results = primaryData.Select(pd => new {
Id = pd.ID,
PrimaryData = pd.PrimaryData,
Extra = Tuple.Create("PhoneNumber", pd.tbList_DataText.Where(ld => ld.DataRowID == pd.ID && ld.ListColumnID == 1).Select(ld => ld.DataField).DefaultIfEmpty("").First())
});
// How to access:
foreach (var result in results)
{
Console.WriteLine(result.Id);
Console.WriteLine(result.PrimaryData);
Console.WriteLine(result.Extra.Item1);
Console.WriteLine(result.Extra.Item2);
}
2)字典
// Using C# 6 notation
var results = primaryData.Select(pd => new Dictionary<string, object>{
["Id"] = pd.ID,
["PrimaryData"] = pd.PrimaryData,
["PhoneNumber"] = pd.tbList_DataText.Where(ld => ld.DataRowID == pd.ID && ld.ListColumnID == 1).Select(ld => ld.DataField).DefaultIfEmpty("").First()
});
// Using C# 5 notation
var results = primaryData.Select(pd => new Dictionary<string, object>{
{"Id", pd.ID},
{"PrimaryData", pd.PrimaryData},
{"PhoneNumber", pd.tbList_DataText.Where(ld => ld.DataRowID == pd.ID && ld.ListColumnID == 1).Select(ld => ld.DataField).DefaultIfEmpty("").First()}
});
// How to access:
foreach(var result in results)
{
Console.WriteLine(result["Id"]);
Console.WriteLine(result["PrimaryData"]);
Console.WriteLine(result["PhoneNumber"]);
}
3)动态
var results = primaryData.Select(pd => {
dynamic result = new System.Dynamic.ExpandoObject();
result.Id = pd.ID;
result.PrimaryData = pd.PrimaryData;
// Choose one of the following. Since you only "PhoneNumber" at runtime, probably the second one.
result.PhoneNumber = pd.tbList_DataText.Where(ld => ld.DataRowID == pd.ID && ld.ListColumnID == 1).Select(ld => ld.DataField).DefaultIfEmpty("").First();
((IDictionary<string, object>)result).Add("PhoneNumber", pd.tbList_DataText.Where(ld => ld.DataRowID == pd.ID && ld.ListColumnID == 1).Select(ld => ld.DataField).DefaultIfEmpty("").First());
return result;
});
// How to access:
foreach(var result in results)
{
Console.WriteLine(result.Id);
Console.WriteLine(result.PrimaryData);
// Both work, independently how you created them
Console.WriteLine(result.PhoneNumber);
Console.WriteLine(((IDictionary<string, object>)result)["PhoneNumber"]);
}
刚从问题中意识到场源也应该是动态的.因此,在上面的代码中,将任何出现的pb.tbList_DataText
替换为:
just realized from question that the field source should be dynamic as well. So, in the above code, replace any occurrence of pb.tbList_DataText
by:
((IEnumerable<X>)pb.GetType().GetField("tbList_DataText").GetValue(pb))
X
应该是ld
的类型.但是要小心!这种转换可能会失败.
Where X
should be the type of ld
. But carefull! This cast can potentially fail.
此外,如果要使用属性而不是字段,只需使用GetProperty
而不是GetField
.
Also, if you want a property instead of a field, just use GetProperty
instead of GetField
.
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