问题：
问：为什么不能/我如何动态使用DataTable中的数据在一个使用反射（？）根据可用内容创建实体实例的函数中制作LINQ / EF？
我见过很多很多Q＆amp;至于硬编码，但没有做这个动态。我正在寻找一种替代方法来维护我所有实体的硬编码代码......
我的方法的背景/验证：
假设： - 我知道类的名称（来自dt.Name），我已经验证了它是一个有效的实体。 - 我知道我将使用每个DataRow更新的列的名称，因为它们位于dt的列名称中。
问题重述，现在有了上下文： 为什么不能/我如何动态使用DataTable中的数据在一个使用反射（？）根据可用内容创建实体实例的函数中制作LINQ / EF？
[Pseudo-Code]
public void DataTableToEntities(DataTable dt){
string entityClassName = dt.Name;
ArrayList/List<string> colNames = dt.Columns. names, ...
....
using (MyContext ctx = new MyContext()){
while (row dtRow in dtRows){
// magic follows:
DeterminedEntity de = new DeterminedEntity();
// populate de with dtRow
ctx.[DeterminedEntity].Add(de);
// magic ends...
}
ctx.SaveChanges;
}
}
理由：
我可以随意添加，编辑和删除实体，而无需像上面那样在导入方案中对这些细微更改进行硬编码。
下一步：处理动态工作簿＆amp;工作表创建为上述过程的上传模板，使用 WorkBook - ＆gt; DataSet 和 WorkSheets - ＆gt;数据表
进度： 2016年11月6日
这个问题的关键似乎是如何从名称中实例化DBContext类的实体实例。
我的Scratch控制台应用程序是一个单独的项目（相同的解决方案），所有模型和＆amp;东西复制过来......
到目前为止，我已经：
static void Main(string[] args)
{
ScratchProgram s = new ScratchConsole1.ScratchProgram();
Console.WriteLine("starting");
string fileLocation = @"C:\Users\...\SomeDbSetClass_test.xlsx";
string tableName = "SomeDbSetClass";
//----------------------------------------------------------
// FreeSpire.xls
Workbook wb = new Workbook();
wb.LoadFromFile(fileLocation);
Console.WriteLine("wb.WorkSheets count: " + wb.Worksheets.Count);
//----------------------------------------------------------
Worksheet ws = wb.Worksheets[tableName];
Console.WriteLine("ws.Rows count: " + ws.Rows.Count());
//----------------------------------------------------------
DataTable dt = new DataTable(tableName);
dt = ws.ExportDataTable();
Console.WriteLine("dt.Rows.Count: " + dt.Rows.Count);
Console.WriteLine("dt.Name: " + dt.TableName);
//==========================================================
string pathToAssembly = @"C:\...\ScratchConsole1.dll";
var aClass = s.CreateInstanceOf(dt.TableName, pathToAssembly);
// Now I have a valid class of the program-NOT the ef ctx...
Console.WriteLine("aClass.FullName: " + aClass.GetType().FullName);
MethodInfo[] aMethods = aClass.GetType().GetMethods();
// now I have an array of all get/sets... "get_<method>" and "set_<method>"
// let's iterate through all the methods, printing them:
for (int i2 = 0;i2 < aMethods.Count() ; i2++)
{
MethodInfo mi = aMethods[i2];
Console.WriteLine("method: " + mi.Name);
}
// the above isn't really useful, as I already have the property names in the dt header row
using (DatabaseContext ctx = new DatabaseContext())
{
//==========================================================
// i is used as column index below, as dr.ItemArray is an array...
int i = 0;
// each dr should create a new instance of the ctx's ef class...
foreach (DataRow dr in dt.Rows)
{
???
...Create new instance in ctx, using as class name: dt.TableName...
ctxClass <--- assuming made using aClass
???
// now we can load each class property with the value from the dr:
foreach (string drItem in dr.ItemArray)
{
Console.WriteLine(String.Format("================= col ================="));
string entAttrName = dt.Columns[i].ToString(); // this is fine as string, but...
string entAttrValue = dr[i].ToString(); // this is NOT <--- see Note1 below
Console.WriteLine("[" + i + "] Item: " + entAttrName.ToString());
Console.WriteLine("[" + i + "] Value: " + entAttrValue.ToString());
???
ctxClass.[entAttrName.ToString()] = entAttrValue.ToString(); <--- see Note1 below
???
//==============================================================================
// Note1:
// the above is far less than ideal, as it has every column/attribute/property type // being used as a String... Obviously, we want to leave doubles as doubles, ints as // ints, etc.
// This becomes a MUCH larger problem when we introduce entities as properties...
// like a State entity with many City entities as a List<State> as a property...
//==============================================================================
i++;
}
ctx.[ef class].Add(ctxClass);
}
ctx.SaveChanges();
}
Console.WriteLine("end.");
Console.ReadKey();
}
public object CreateInstanceOf(string ClassName, string AssemblyFullPath)
{
var assemblyFullPath = Assembly.LoadFrom(@"C:\...\ScratchConsole1.exe");
var assembly = Assembly.GetExecutingAssembly();
var type = assembly.GetTypes().First(t => t.Name == ClassName);
return Activator.CreateInstance(type);
}
我希望这会让事情变得更容易理解。:)
更新和解决方案！ SO用户Gert Arnold通过在this post上更改了一行来解决了问题：
// All details from the property to update/set:
//PropertyInfo theProp = thisTypeInfo.GetDeclaredProperty(entAttrName);
PropertyInfo theProp = thisTypeInfo.GetProperty(entAttrName);
格特的解释：
thisTypeInfo.GetDeclaredProperty获取该类型声明的属性 本身，而不是它的超类型。使用thisTypeInfo.GetProperty。 - 格特阿诺德
我无法相信我能够以一种聪明人可以解决的方式解决我几乎无法理解的问题！
=============================================== ============================
答案 0 :(得分：2)
这里的解决方案：
此程序采用电子表格文件（.xlsx），读取EF DbSet类的选项卡名称，以及列名称＆amp;属性名称和值的值，并将它们保存为EF安装的数据存储中的单个实体（适用于SQLite和SQL Server 2014）。
很酷的部分是，在EF类名，属性等应用程序中不需要硬编码。这意味着你可以创建一个Excel 模板，让某人填写它（只是你在模板中给出它们的列，并且可以毫不费力地导入该文件。
您需要为自己重新创建的所有内容都在这篇文章中。
我想要这个用于我自己的应用程序我正在写作，并且有点惊讶没有人想要做同样的事情。有了100多个EF类和基类，答案（甚至在这里）是笨拙的，咬紧牙关，硬编码一切。
我将尽可能完整地发布工作代码。对于任何试图使其软件更易于使用的人来说，这段代码有望向前迈进一大步。为了完全隔离问题/ Poc / Answer，我使用了：
VS 2015，SQLite最新版，SQLite.CodeFirst，System.Data.SQLite [.Linq和.EF6]（＆lt; - 可能不是全部都需要，但我第一次与SQLite斗争），NLog，NLog.Config， Spire.XLS，EF6 ......应该是它。一切都在NuGet完成。
注意：
- 我在普通系统中使用SQL 2014 Ent，但发现SQLite具有相同的性能。实际上，下面的示例和时间是在SQLite数据库文件上！
- 下面的时间是我的开发笔记本电脑，它在VirtBox虚拟机上运行Win10，上面有VS2015。同一台笔记本电脑上的另一台VM正在运行SQL 2014 Enterprise，但是对于这个测试示例，我在同一台Win10 VM上使用了SQLite
- 我的 MyDbContext.cs 和 Configuration.cs 文件是裸骨，没有播种等。
public DbSet<Person> Persons { get; set; }
public DbSet<Child> Children { get; set; }
- 有一个简单的test.xlsx文件，其中包含要插入DB的值。
这是它的.csv：
sChildFoo,iChildBar,dChildBaz,PersonAge,PersonWeight,PersonName
Norwich,29884,1.2,34,123,Fred Flintstone
Waterford,34990,3.4,56,210,Barney Rubble
重要提示：工作表中的标签标记为子级 - 与您希望加载值的类完全相同。有2个数据/实体类，Person（）和Child（）称为 PersonChild.cs ：
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace DynamicEFLoading
{
public abstract class Person
{
[Key]
public int PersonId { get; set; }
public int PersonAge { get; set; }
public int PersonWeight { get; set; }
public string PersonName { get; set; }
}
class Child : Person
{
[Key]
[Column(Order = 0)]
public int Id { get; set; }
public string sChildFoo { get; set; }
public int iChildBar { get; set; }
public double dChildBaz { get; set; }
}
}
所有Child（）实例都从Person（）继承属性，如您所见。我甚至将Person（）抽象化了。
这是物质，正如我在评论中所说的那样装饰， TestProgram.cs ：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.SQLite;
using NLog;
using System.Reflection;
using System.Data.Entity;
using Spire.Xls;
using System.Data;
using System.Collections;
namespace DynamicEFLoading
{
class TestProgram
{
private static Logger logit = LogManager.GetCurrentClassLogger();
static void Main()
{
DateTime dtStart = new DateTime(DateTime.Now.Ticks);
DateTime dtStop = new DateTime();
TestProgram s = new TestProgram();
Utils u = new Utils();
s.p("Starting at " + DateTime.Now.ToLongTimeString());
// for this test, I leave this door open the whole time...
using (MyDbContext ctx = new MyDbContext())
{
//###########################################################################
//
// create a row in db each time run...
//
Random rnd = new Random();
//
Child c1 = new DynamicEFLoading.Child();
// Age, Weight, Name all come from base class Person()
c1.PersonAge = rnd.Next(120);
c1.PersonWeight = rnd.Next(85, 300);
c1.PersonName = String.Format("{0} {1}", Utils.GenerateName(6), Utils.GenerateName(8));
s.p(String.Format("Created .Name: {0}", c1.PersonName));
//
c1.dChildBaz = rnd.NextDouble();
c1.iChildBar = rnd.Next(99999);
c1.sChildFoo = String.Format("{0}", Utils.GenerateName(10));
s.p(String.Format("Created .sParentFoo: {0}", c1.sChildFoo));
//
ctx.Children.Add(c1);
//_______________________________________________________
ctx.SaveChanges();
//###########################################################################
//
// in production, there would be no hard coding...
//
string fileLocation = @"C:\Users\<some user>\Desktop\test.xlsx";
//
// NOTE! Here I am specifying the only tab(ws name) in the wb. This is easily changed
// to access all tabs by index, using Worksheet ws = wb.Worksheets[index], and
// a simple loop through them all. In my first test, I even verify the tab had
// a corresponding table in DB before continuing...
string tableName = "Child";
//----------------------------------------------------------
// freeSpire.xls
Workbook wb = new Workbook();
wb.LoadFromFile(fileLocation);
//----------------------------------------------------------
// see NOTE! just above...
Worksheet ws = wb.Worksheets[tableName];
//----------------------------------------------------------
// create a DataTable
DataTable dt = new DataTable(tableName);
// load it with data from whoile worksheet (ws)
dt = ws.ExportDataTable();
// from now on, we use DataTable-not spreadsheet
//----------------------------------------------------------
s.p(String.Format("wb.WorkSheets count: " + wb.Worksheets.Count));
s.p(String.Format("ws.Rows count: " + ws.Rows.Count()));
s.p(String.Format("dt.Rows.Count: " + dt.Rows.Count));
s.p(String.Format("dt.Name: " + dt.TableName));
//==========================================================
// getting assembly name programmatically fails when a project is inside a solution
// in VS. It assumes ...\ProjName\ProjName\... whis isn't how solutions go...
string pathToAssembly = @"C:\Users\<some user>\Documents\Visual Studio 2015\Projects\DynamicEFLoading\DynamicEFLoading\bin\Debug\DynamicEfLoading.exe";
// string pathToAssembly = @".\DynamicEfLoading.exe";
// create an 'anonymous', or ghost class:
var aClass = u.CreateInstanceOf(dt.TableName, pathToAssembly);
// display class type
s.p(String.Format("aClass.FullName: " + aClass.GetType().FullName));
//==========================================================
//
// creating a DbSet for the dt's entities. It isn't good enough to just create
// the class itself-it needs to be from the DbContext (ctx). or else you can't
// ctx.SaveChanges();
//
s.p(String.Format("Creating 'dbs' object..."));
DbSet dbs = ctx.Set(aClass.GetType());
// But you can't att attributes/properties to a DbSet-only to the class it is
// derived from, so we then use the DbSet (dbs) for this class to create an
// empty class that we can populate & later add to DB via ctx:
var theObj = dbs.Create(aClass.GetType());
// make sure it's the right one:
s.p(String.Format("GetType: " + theObj.GetType()));
//____________________________________________________________________________
int i = 0; // used to keep track of each column as we go through the dt
foreach (DataRow dr in dt.Rows) // each dr in the dt is a separate instance of the theObj class
{
s.p(String.Format("================= row =================================="));
i = 0; // I don't like to put var instantiation in a loop...
// each drItem is the content for the row (theObj)
foreach (string drItem in dr.ItemArray)
{
s.p(String.Format("================= col {0} ", i));
string entAttrName = dt.Columns[i].ToString();
string entAttrValue = dr[i].ToString();
// column (property) name:
s.p("[" + i + "] Item: " + entAttrName.ToString());
// the value of that property to load into this class' property
s.p("[" + i + "] Value: " + entAttrValue.ToString());
// which type of data is this property? (string, int32, double...)
// -also has data like if nullable, etc. of use in later refinements...
TypeInfo thisTypeInfo = theObj.GetType().GetTypeInfo();
// All details from the property to update/set:
PropertyInfo theProp = thisTypeInfo.GetProperty(entAttrName);
//___________________________________________________________________
// need to determine the property type, converting entAttrValuefrom string:
// good debugging info at this stage to see what we've discovered from the class dynamically at rn time...
s.p("theProp.DeclaringType.FullName of attr: " + theProp.DeclaringType.FullName);
s.p("theProp.GetSetMethod(true).ToString() of attr: " + theProp.GetSetMethod(true).ToString());
s.p("theProp.GetType().ToString() of attr: " + theProp.GetType().ToString());
s.p("theProp.Name of attr: " + theProp.Name);
s.p("theProp.PropertyType.ToString() of attr: " + theProp.PropertyType.ToString());
s.p("theProp.ReflectedType.ToString() of attr: " + theProp.ReflectedType.ToString());
s.p("theProp.ReflectedType.ToString() of attr: " + theProp.SetMethod.ReturnType.ToString());
/* update entAttrName with entAttrValue:
*
* At this point, my values in the DataTable are all strings, but the class itself
* stores that value as who-knows-what. So here I just parse out what kind it is from three
* common types. In future, may need to add more, but for now, these are the big 4:
*
* String, Integer, DatTime, and Double
*/
if (theProp.PropertyType.ToString() == "System.String")
{
theProp.SetValue(theObj, (String)entAttrValue);
logit.Debug("Set {0} value: {1}",
theProp.PropertyType.ToString(),
entAttrValue);
}
else if (theProp.PropertyType.ToString().Contains("System.Int32"))
{
theProp.SetValue(theObj, int.Parse(entAttrValue));
logit.Debug("Set {0} value: {1}",
theProp.PropertyType.ToString(),
entAttrValue);
}
else if (theProp.PropertyType.ToString().Contains("System.DateTime"))
{
IFormatProvider culture = new System.Globalization.CultureInfo("en-US", true);
DateTime dTime = DateTime.Parse(entAttrValue, culture, System.Globalization.DateTimeStyles.AssumeLocal);
theProp.SetValue(theObj, entAttrValue);
logit.Debug("Set {0} value: {1}",
theProp.PropertyType.ToString(),
entAttrValue);
}
else if (theProp.PropertyType.ToString().Contains("System.Double"))
{
theProp.SetValue(theObj, double.Parse(entAttrValue));
logit.Debug("Set {0} value: {1}",
theProp.PropertyType.ToString(),
entAttrValue);
}
else
{
logit.Error("Unexpected property type: {0} given. string value: {1}",
theProp.PropertyType.ToString(),
entAttrValue
);
}
i++; // increment column index...
} // end foreach (string drItem in dr.ItemArray...
// add class to context...
dbs.Add(theObj);
// to save one by one (each row):
ctx.SaveChanges();
} // end of foreach (DataRow dr in dt.Rows...
// or... to save as batch (at end of worksheet):
// ctx.SaveChanges();
//###########################################################################
dtStop = new DateTime(DateTime.Now.Ticks);
TimeSpan tsDuration = dtStop - dtStart;
s.p(String.Format("end... took {0} seconds.", tsDuration.TotalSeconds.ToString()));
Console.ReadKey();
} // end using DbContext...
}
/*
* Convenience; writes to both...
*
*/
//private static void p(string message)
private void p(string message)
{
logit.Info(message);
Console.WriteLine(message);
}
}
}
最后，这是包含Utils（）类的 Utils.cs 文件。您可以在上面将这些称为“u。*”，在TestProgram.cs顶部实例化的方式：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;
using NLog;
using System.Collections;
using System.Data;
namespace DynamicEFLoading
{
class Utils
{
private static Logger logit = LogManager.GetCurrentClassLogger();
public ArrayList HeadersFromDataTable(DataTable theDataTable)
{
ArrayList arHeaders = new ArrayList();
try
{
arHeaders.AddRange(theDataTable.Columns);
logit.Info("loaded {0} column headers...", arHeaders.Count);
}
catch (Exception ex)
{
logit.Fatal("exception: " + ex.ToString());
}
return arHeaders;
}
public object CreateInstanceOf(string ClassName, string AssemblyFullPath)
{
var assemblyFullPath = Assembly.LoadFrom(@"C:\Users\<some user>\Documents\Visual Studio 2015\Projects\PoliticWebSite\ScratchConsole1\bin\Debug\ScratchConsole1.exe");
var assembly = Assembly.GetExecutingAssembly();
//var assembly = Assembly.LoadFrom(assemblyFullPath);
var type = assembly.GetTypes().First(t => t.Name == ClassName);
return Activator.CreateInstance(type);
}
public static string GenerateName(int len)
{
Random rndSeed = new Random(DateTime.Now.Millisecond);
Random r = new Random(rndSeed.Next());
string[] consonants = { "b", "c", "d", "f", "g", "h", "j", "k", "l", "m", "l", "n", "p", "q", "r", "s", "sh", "zh", "t", "v", "w", "x" };
string[] vowels = { "a", "e", "i", "o", "u", "ae", "y" };
string Name = "";
Name += consonants[r.Next(consonants.Length)].ToUpper();
Name += vowels[r.Next(vowels.Length)];
int b = 2; //b tells how many times a new letter has been added. It's 2 right now because the first two letters are already in the name.
while (b < len)
{
//_________________________________________________________________
rndSeed = new Random(DateTime.Now.Millisecond);
r = new Random(rndSeed.Next());
Name += consonants[r.Next(consonants.Length)];
b++;
//_________________________________________________________________
rndSeed = new Random(DateTime.Now.Millisecond);
r = new Random(rndSeed.Next());
Name += vowels[r.Next(vowels.Length)];
b++;
//_________________________________________________________________
}
return Name;
}
}
}
那么所有这些看起来是什么样的，因为程序遍历每一列（可以按任何顺序，BTW）？
2016-11-08 22:18:14.2500 INFO Starting at 10:18:14 PM
2016-11-08 22:18:14.3499 INFO Created .Name: Tytaetae Tytaetaetae
2016-11-08 22:18:14.3499 INFO Created .sParentFoo: Baebabababa
2016-11-08 22:18:15.2181 INFO wb.WorkSheets count: 2
2016-11-08 22:18:15.2181 INFO ws.Rows count: 3
2016-11-08 22:18:15.2338 INFO dt.Rows.Count: 2
2016-11-08 22:18:15.2338 INFO dt.Name: Child
2016-11-08 22:18:15.2487 INFO aClass.FullName: DynamicEFLoading.Child
2016-11-08 22:18:15.2487 INFO Creating 'dbs' object...
2016-11-08 22:18:15.2644 INFO GetType: DynamicEFLoading.Child
2016-11-08 22:18:15.2644 INFO ================= row ==================================
2016-11-08 22:18:15.2644 INFO ================= col 0
2016-11-08 22:18:15.2801 INFO [0] Item: sChildFoo
2016-11-08 22:18:15.2801 INFO [0] Value: Norwich
2016-11-08 22:18:15.2801 INFO theProp.DeclaringType.FullName of attr: DynamicEFLoading.Child
2016-11-08 22:18:15.2958 INFO theProp.GetSetMethod(true).ToString() of attr: Void set_sChildFoo(System.String)
2016-11-08 22:18:15.2958 INFO theProp.GetType().ToString() of attr: System.Reflection.RuntimePropertyInfo
2016-11-08 22:18:15.3114 INFO theProp.Name of attr: sChildFoo
2016-11-08 22:18:15.3114 INFO theProp.PropertyType.ToString() of attr: System.String
2016-11-08 22:18:15.3271 INFO theProp.ReflectedType.ToString() of attr: DynamicEFLoading.Child
2016-11-08 22:18:15.3271 INFO theProp.ReflectedType.ToString() of attr: System.Void
2016-11-08 22:18:15.3271 DEBUG Set System.String value: Norwich
2016-11-08 22:18:15.3428 INFO ================= col 1
...
2016-11-08 22:18:16.1237 INFO ================= row ==================================
2016-11-08 22:18:16.1394 INFO ================= col 0
2016-11-08 22:18:16.1394 INFO [0] Item: sChildFoo
2016-11-08 22:18:16.1551 INFO [0] Value: Waterford
2016-11-08 22:18:16.1551 INFO theProp.DeclaringType.FullName of attr: DynamicEFLoading.Child
2016-11-08 22:18:16.1551 INFO theProp.GetSetMethod(true).ToString() of attr: Void set_sChildFoo(System.String)
2016-11-08 22:18:16.1707 INFO theProp.GetType().ToString() of attr: System.Reflection.RuntimePropertyInfo
2016-11-08 22:18:16.1863 INFO theProp.Name of attr: sChildFoo
2016-11-08 22:18:16.1863 INFO theProp.PropertyType.ToString() of attr: System.String
2016-11-08 22:18:16.1863 INFO theProp.ReflectedType.ToString() of attr: DynamicEFLoading.Child
2016-11-08 22:18:16.2020 INFO theProp.ReflectedType.ToString() of attr: System.Void
2016-11-08 22:18:16.2020 DEBUG Set System.String value: Waterford
2016-11-08 22:18:16.2179 INFO ================= col 1
...
2016-11-08 22:18:16.5772 INFO ================= col 5
2016-11-08 22:18:16.5772 INFO [5] Item: PersonName
2016-11-08 22:18:16.5772 INFO [5] Value: Barney Rubble
2016-11-08 22:18:16.5772 INFO theProp.DeclaringType.FullName of attr: DynamicEFLoading.Person
2016-11-08 22:18:16.5927 INFO theProp.GetSetMethod(true).ToString() of attr: Void set_PersonName(System.String)
2016-11-08 22:18:16.5927 INFO theProp.GetType().ToString() of attr: System.Reflection.RuntimePropertyInfo
2016-11-08 22:18:16.5927 INFO theProp.Name of attr: PersonName
2016-11-08 22:18:16.6084 INFO theProp.PropertyType.ToString() of attr: System.String
2016-11-08 22:18:16.6084 INFO theProp.ReflectedType.ToString() of attr: DynamicEFLoading.Child
2016-11-08 22:18:16.6240 INFO theProp.ReflectedType.ToString() of attr: System.Void
2016-11-08 22:18:16.6240 DEBUG Set System.String value: Barney Rubble
2016-11-08 22:18:16.6397 INFO end... took 2.391686 seconds.
加载文件2.4秒，将其解析为DataSet / DataTable，然后将它们转换为类和EF实例，检查每列的有效性。全部在Linux笔记本电脑上的Win10 VM中
现在，我提供你（我的杂乱和低效）解决方案来抓住＆amp;保存EF数据，无需硬编码除Excel模板的标题行之外的任何内容。
要-DOS：
-add循环遍历工作簿，完成所有工作表
在数据表中指示的-add验证类实际上存在于EF中（我在我的导频代码中执行此操作）
-add验证文件是导入前的有效.xlsx文件（Spire具有此功能）等。
我花了很多时间才能使它工作，而且由于我从正常的编程中走过头来，我会很感激任何关于使其变得更好/更安全等的反馈。我通过绊倒Intellisense和书籍来做到这一点，主要是。
=============================================== ===================