What is reflection in c#?

Here have a Runtime error and it for Can not be an object of type "System.Runtime.TargetedPatchingOptOutAttribute" is cast to type "BugFixApplication.DeBugInfo".

using System;

using System.Reflection;

namespace BugFixApplication

{//a custom attribute BugFix to be

//assigned to a class and its members

[AttributeUsage(AttributeTargets.Class |

AttributeTargets.Constructor |

AttributeTargets.Field |

AttributeTargets.Method |

AttributeTargets.Property,

AllowMultiple = true)]

public class DeBugInfo : System.Attribute

{

private int bugNo;

private string developer;

private string lastReview;

public string message;

public DeBugInfo(int bg, string dev, string d)

{

this.bugNo = bg;

this.developer = dev;

this.lastReview = d;

}

public int BugNo

{

get

{

return bugNo;

}

public string Developer

{

get

{

return developer;

}

public string LastReview

{

get

{

return lastReview;

}

public string Message

{

get

{

return message;

}

set

{

message = value;

}

[DeBugInfo(45, "Zara Ali", "12/8/2012",

Message = "Return type mismatch")]

[DeBugInfo(49, "Nuha Ali", "10/10/2012",

Message = "Unused variable")]

class Rectangle

{

//member variables

protected double length;

protected double width;

public Rectangle(double l, double w)

{

length = l;

width = w;

}

[DeBugInfo(55, "Zara Ali", "19/10/2012",

Message = "Return type mismatch")]

public double GetArea()

{

return length * width;

}

[DeBugInfo(56, "Zara Ali", "19/10/2012")]

public void Display()

{

Console.WriteLine("Length: {0}", length);

Console.WriteLine("Width: {0}", width);

Console.WriteLine("Area: {0}", GetArea());

}

}//end class Rectangle

class ExecuteRectangle

{

static void Main(string[] args)

{

Rectangle r = new Rectangle(4.5, 7.5);

r.Display();

Type type = typeof(Rectangle);

//iterating through the attribtues of the Rectangle class

foreach (Object attributes in type.GetCustomAttributes(false))

{

DeBugInfo dbi = (DeBugInfo)attributes;

if (null != dbi)

{

Console.WriteLine("Bug no: {0}", dbi.BugNo);

Console.WriteLine("Developer: {0}", dbi.Developer);

Console.WriteLine("Last Reviewed: {0}",

dbi.LastReview);

Console.WriteLine("Remarks: {0}", dbi.Message);

}

//iterating through the method attribtues

foreach (MethodInfo m in type.GetMethods())

{

foreach (Attribute a in m.GetCustomAttributes(true))

{

DeBugInfo dbi = (DeBugInfo)a; // Here have a Runtime error.

if (null != dbi)

{

Console.WriteLine("Bug no: {0}, for Method: {1}",

dbi.BugNo, m.Name);

Console.WriteLine("Developer: {0}", dbi.Developer);

Console.WriteLine("Last Reviewed: {0}",

dbi.LastReview);

Console.WriteLine("Remarks: {0}", dbi.Message);

}

Console.ReadLine();

}

Reflection provides objects (of type Type) that describe assemblies, modules and types. You can use reflection to dynamically create an instance of a type, bind the type to an existing object, or get the type from an existing object and invoke its methods or access its fields and properties. If you are using attributes in your code, reflection enables you to access them. For more information, see Extending Metadata Using Attributes.

Here's a simple example of reflection using the static method GetType - inherited by all types from the Object base class - to obtain the type of a variable:

// Using GetType to obtain type information:  int i = 42; System.Type type = i.GetType(); System.Console.WriteLine(type);

4 Replies

Know the answer? Post it — somebody with the same question will find it here.

Abhay Shanker12y ago
Check the below link also, will be helpful to you

http://www.dotnetperls.com/reflection
http://www.codeproject.com/Articles/17269/Reflection-in-C-Tutorial
http://www.csharp-examples.net/reflection-examples/
Ken H12y ago
Here have a Runtime error and it for Can not be an object of type "System.Runtime.TargetedPatchingOptOutAttribute" is cast to type "BugFixApplication.DeBugInfo".

using System;
using System.Reflection;

namespace BugFixApplication
{//a custom attribute BugFix to be
//assigned to a class and its members
[AttributeUsage(AttributeTargets.Class |
AttributeTargets.Constructor |
AttributeTargets.Field |
AttributeTargets.Method |
AttributeTargets.Property,
AllowMultiple = true)]

public class DeBugInfo : System.Attribute
{
private int bugNo;
private string developer;
private string lastReview;
public string message;

public DeBugInfo(int bg, string dev, string d)
{
this.bugNo = bg;
this.developer = dev;
this.lastReview = d;
}

public int BugNo
{
get
{
return bugNo;
}
}
public string Developer
{
get
{
return developer;
}
}
public string LastReview
{
get
{
return lastReview;
}
}
public string Message
{
get
{
return message;
}
set
{
message = value;
}
}
}
[DeBugInfo(45, "Zara Ali", "12/8/2012",
Message = "Return type mismatch")]
[DeBugInfo(49, "Nuha Ali", "10/10/2012",
Message = "Unused variable")]
class Rectangle
{
//member variables
protected double length;
protected double width;
public Rectangle(double l, double w)
{
length = l;
width = w;
}
[DeBugInfo(55, "Zara Ali", "19/10/2012",
Message = "Return type mismatch")]
public double GetArea()
{
return length * width;
}
[DeBugInfo(56, "Zara Ali", "19/10/2012")]
public void Display()
{
Console.WriteLine("Length: {0}", length);
Console.WriteLine("Width: {0}", width);
Console.WriteLine("Area: {0}", GetArea());
}
}//end class Rectangle

class ExecuteRectangle
{
static void Main(string[] args)
{
Rectangle r = new Rectangle(4.5, 7.5);
r.Display();
Type type = typeof(Rectangle);
//iterating through the attribtues of the Rectangle class
foreach (Object attributes in type.GetCustomAttributes(false))
{
DeBugInfo dbi = (DeBugInfo)attributes;
if (null != dbi)
{
Console.WriteLine("Bug no: {0}", dbi.BugNo);
Console.WriteLine("Developer: {0}", dbi.Developer);
Console.WriteLine("Last Reviewed: {0}",
dbi.LastReview);
Console.WriteLine("Remarks: {0}", dbi.Message);
}
}

//iterating through the method attribtues
foreach (MethodInfo m in type.GetMethods())
{
foreach (Attribute a in m.GetCustomAttributes(true))
{
DeBugInfo dbi = (DeBugInfo)a; // Here have a Runtime error.
if (null != dbi)
{
Console.WriteLine("Bug no: {0}, for Method: {1}",
dbi.BugNo, m.Name);
Console.WriteLine("Developer: {0}", dbi.Developer);
Console.WriteLine("Last Reviewed: {0}",
dbi.LastReview);
Console.WriteLine("Remarks: {0}", dbi.Message);
}
}
}
Console.ReadLine();
}
}
}
Abhishek Jaiswal12y ago
heyy ken

go through this link to undetstand this concept better, with example:
http://www.tutorialspoint.com/csharp/csharp_reflection.htm

:) :)
Nhlanhla A W Mkhize12y ago
Reflection provides objects (of type Type) that describe assemblies, modules and types. You can use reflection to dynamically create an instance of a type, bind the type to an existing object, or get the type from an existing object and invoke its methods or access its fields and properties. If you are using attributes in your code, reflection enables you to access them. For more information, see Extending Metadata Using Attributes.

Here's a simple example of reflection using the static method GetType - inherited by all types from the Object base class - to obtain the type of a variable:
```
// Using GetType to obtain type information:  int i = 42; System.Type type = i.GetType(); System.Console.WriteLine(type);
```