Usefull Attribute of c#
Usefull Attribute of c#
Recently, I have finished a project of sms.
The protocol of pdu is cmpp.
There are a lot of handy source codes available for me. But I decided to build it from scratch.
In the protocol of cmpp, a pdu is made up of a header and a body, the fields of a header are defined as follow:
|
Field name |
Data type |
Length |
Description |
|
TotalLen |
UnsignedInteger |
4 |
The totol length of a pdu. |
|
CmdID |
UnsignedInteger |
4 |
The command type identifier |
|
SeqNum |
UnsignedInteger |
4 |
The sequence number of a pdu. |
The body fields depend on the value of CmdID in the header. But the form of the fields are just like those in the header.
To describe a pdu, it’s nature that I made a base class like this:
// CmppMessage.cs
public abstract class CmppMessage
{
public int TotalLen;
public int CmdID;
public int SeqNum;
}
Then the problem comes: I lost the information such as, Data Type, Length, etc.
When I know there is an attribute thing in c#, I was very excited. I knew the problem may be resolved perfectly.
An attribute named CmppFieldAttribute was created to keep the information of the field of CmppMessage.
// CmppFieldAttribute.cs
[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field)]
public class CmppFieldAttribute:System.Attribute
{
CmppFieldType m_Type;
int m_Len;
public CmppFieldAttribute(CmppFieldType type,int len)
{
m_Type = type;
m_Len = len;
}
public CmppFieldType FieldType
{
get{return m_Type;}
set{m_Type = value;}
}
public int Length
{
get{ return m_Len;}
set{ m_Len = value;}
}
}
Hence, my abstract base class becomes:
public abstract class CmppMessage
{
[CmppField(CmppFieldType.UnsignedInteger, 4)]
public int TotalLen;
[CmppField(CmppFieldType.UnsignedInteger, 4)]
public int CmdID;
[CmppField(CmppFieldType.UnsignedInteger, 4)]
public int SeqNum;
}
In my final source code there are a lot more property in CmppFieldAttribute class. But the above already show my idea completely.
