This constructor executes?-CodePudding

List _As;
_As=_DbCnn. Query (SQL). ToList ();//this is a collection of database query out

Object A has A constructor
The public (A)
{
_B=new B ();
}
Excuse me _As=_DbCnn. Query (SQL). ToList (); This assignment, the object A constructor executes?

CodePudding user response:

You're not yourself next breakpoint??

CodePudding user response:

Does not perform, not instantiate objects, such assignment is an error, not the instance reference to the object,

CodePudding user response:

In principle, if a class can be instantiated smoothly. There must be a constructor to perform, either a parameterless constructor, either has a constructor parameters,

CodePudding user response:

reference 3 floor closure guest response:

according to the truth, if a class can be instantiated smoothly. There must be a constructor to perform, either a parameterless constructor, either has a constructor parameters,

Some ORM framework will avoid the constructor, the intention may be to avoid the additional constructor logic,
Since dotnet1.1, actually can use FormatterServices. Get Uninitialized Object (Type) to create an Object constructor don't use it,
Dotnet Remoting BinaryFormatter also internal use FormatterServices. GetUninitializedObject to ward off the constructor to inverse series of possible side effects,

 using System; 
Using System. IO; 
Using System. The Runtime. Serialization; 
Using System. The Runtime. Serialization. Formatters. Binary; 

Class Program 
{
//in Dotnet Framework 4.0 compiler running under the 
The static void Main (string [] args) 
{
My my1=new My ();//calls the constructor, and the output 'My constructed! Id=123 '

BinaryFormatter bf=new BinaryFormatter (); 
MemoryStream ms=new MemoryStream (); 
Bf. Serialize (ms, my1); 

Ms. Position=0; 
My my2=(My) bf. Deserialize (ms).//not calls the constructor 
My2. Id=888; 
Console. WriteLine (" my1. Id={0}; My2. Id={1} ", my1. Id, my2. Id); 
Ms. The Dispose (); 



Console. WriteLine (" another way "); 
The Console. ReadLine (); 

My my3=(My) FormatterServices. GetUninitializedObject (typeof (My));//not calls the constructor, but has been allocated space needed 
Console. WriteLine (" my3. Id={0}; ", my3. Id);//my3. Id=0 
} 
} 

[Serializable] 
The class My 
{
Public My () 
{
Id=123; 
Console. WriteLine (" My constructed! Id="+ Id); 
} 
Public int Id {get; The set; } 
}