我有一个类，它看起来像这样:
public class Field
{
public string FieldName;
public string FieldType;
}
和一个对象列表<字段>值:
{"EmployeeID","int"},
{"EmployeeName","String"},
{"Designation","String"}
我想创建一个类，看起来像这样:
Class DynamicClass
{
int EmployeeID,
String EmployeeName,
String Designation
}
有什么办法可以做到吗?
我希望它在运行时生成。我不希望在文件系统中驻留一个物理CS文件。
当前回答
哇!谢谢你的回答!我添加了一些功能，以创建一个“数据表到json”的转换器，我与您分享。
Public Shared Sub dt2json(ByVal _dt As DataTable, ByVal _sb As StringBuilder)
Dim t As System.Type
Dim oList(_dt.Rows.Count - 1) As Object
Dim jss As New JavaScriptSerializer()
Dim i As Integer = 0
t = CompileResultType(_dt)
For Each dr As DataRow In _dt.Rows
Dim o As Object = Activator.CreateInstance(t)
For Each col As DataColumn In _dt.Columns
setvalue(o, col.ColumnName, dr.Item(col.ColumnName))
Next
oList(i) = o
i += 1
Next
jss = New JavaScriptSerializer()
jss.Serialize(oList, _sb)
End Sub
在"compileresulttype" sub中，我修改了:
For Each column As DataColumn In _dt.Columns
CreateProperty(tb, column.ColumnName, column.DataType)
Next
Private Shared Sub setvalue(ByVal _obj As Object, ByVal _propName As String, ByVal _propValue As Object)
Dim pi As PropertyInfo
pi = _obj.GetType.GetProperty(_propName)
If pi IsNot Nothing AndAlso pi.CanWrite Then
If _propValue IsNot DBNull.Value Then
pi.SetValue(_obj, _propValue, Nothing)
Else
Select Case pi.PropertyType.ToString
Case "System.String"
pi.SetValue(_obj, String.Empty, Nothing)
Case Else
'let the serialiser use javascript "null" value.
End Select
End If
End If
End Sub
其他回答
运行时代码生成与JVM和CLR - 彼得Sestoft
为真正对这类编程感兴趣的人工作。
我给你的建议是，如果你声明了一些东西，尽量避免字符串，所以如果你有类Field，最好使用类System。类型来存储字段类型而不是字符串。 为了最好的解决方案，而不是创建新的类，尝试使用那些已经创建的FiledInfo，而不是创建新的。
您可以考虑使用动态模块和类来完成这项工作。唯一的缺点是它仍然加载在应用程序域中。但是。net 4.0支持可收集的动态程序集，因此你可以动态地重新创建类/类型。
你可以使用system . runtime . remoting . agents . realproxy。它将允许您使用“正常”代码，而不是低级程序集类型的东西。
请参阅RealProxy对这个问题的回答，以获得一个好例子:
我如何拦截一个方法调用在c# ?
您还可以使用DynamicObject动态创建类。
public class DynamicClass : DynamicObject
{
private Dictionary<string, KeyValuePair<Type, object>> _fields;
public DynamicClass(List<Field> fields)
{
_fields = new Dictionary<string, KeyValuePair<Type, object>>();
fields.ForEach(x => _fields.Add(x.FieldName,
new KeyValuePair<Type, object>(x.FieldType, null)));
}
public override bool TrySetMember(SetMemberBinder binder, object value)
{
if (_fields.ContainsKey(binder.Name))
{
var type = _fields[binder.Name].Key;
if (value.GetType() == type)
{
_fields[binder.Name] = new KeyValuePair<Type, object>(type, value);
return true;
}
else throw new Exception("Value " + value + " is not of type " + type.Name);
}
return false;
}
public override bool TryGetMember(GetMemberBinder binder, out object result)
{
result = _fields[binder.Name].Value;
return true;
}
}
我将所有类字段连同它们的类型和值一起存储在字典_fields中。这两种方法都可以获取或设置一些属性的值。必须使用dynamic关键字创建该类的实例。
使用你的例子:
var fields = new List<Field>() {
new Field("EmployeeID", typeof(int)),
new Field("EmployeeName", typeof(string)),
new Field("Designation", typeof(string))
};
dynamic obj = new DynamicClass(fields);
//set
obj.EmployeeID = 123456;
obj.EmployeeName = "John";
obj.Designation = "Tech Lead";
obj.Age = 25; //Exception: DynamicClass does not contain a definition for 'Age'
obj.EmployeeName = 666; //Exception: Value 666 is not of type String
//get
Console.WriteLine(obj.EmployeeID); //123456
Console.WriteLine(obj.EmployeeName); //John
Console.WriteLine(obj.Designation); //Tech Lead
编辑:下面是我的类Field的外观:
public class Field
{
public Field(string name, Type type)
{
this.FieldName = name;
this.FieldType = type;
}
public string FieldName;
public Type FieldType;
}
哇!谢谢你的回答!我添加了一些功能，以创建一个“数据表到json”的转换器，我与您分享。
Public Shared Sub dt2json(ByVal _dt As DataTable, ByVal _sb As StringBuilder)
Dim t As System.Type
Dim oList(_dt.Rows.Count - 1) As Object
Dim jss As New JavaScriptSerializer()
Dim i As Integer = 0
t = CompileResultType(_dt)
For Each dr As DataRow In _dt.Rows
Dim o As Object = Activator.CreateInstance(t)
For Each col As DataColumn In _dt.Columns
setvalue(o, col.ColumnName, dr.Item(col.ColumnName))
Next
oList(i) = o
i += 1
Next
jss = New JavaScriptSerializer()
jss.Serialize(oList, _sb)
End Sub
在"compileresulttype" sub中，我修改了:
For Each column As DataColumn In _dt.Columns
CreateProperty(tb, column.ColumnName, column.DataType)
Next
Private Shared Sub setvalue(ByVal _obj As Object, ByVal _propName As String, ByVal _propValue As Object)
Dim pi As PropertyInfo
pi = _obj.GetType.GetProperty(_propName)
If pi IsNot Nothing AndAlso pi.CanWrite Then
If _propValue IsNot DBNull.Value Then
pi.SetValue(_obj, _propValue, Nothing)
Else
Select Case pi.PropertyType.ToString
Case "System.String"
pi.SetValue(_obj, String.Empty, Nothing)
Case Else
'let the serialiser use javascript "null" value.
End Select
End If
End If
End Sub
