C# example of how to use key-value pairs to replace the Switch...Case statement

swich....case If there are too many conditional branches, it will seriously damage the beauty of the program.
For example, this

The above code is used for communication between two processes. Since there are many enumerations for communication, there are many case branches. As a result, the readability and maintainability of the code are seriously reduced. After searching for information and reconstructing, I came up with a feasible alternative to switch...case in this situation——using key-value pairs.

Declare key-value pair objects

For the code logic of process communication, the following key-value pairs are constructed.

Dictionary<EnumMsg, Action<Message>> mMessageReceiver = new Dictionary<EnumMsg, Action<Message>>();

The key of this key-value pair is a custom message enumeration, and the value is the delegate of Action<Message>. In this way, the message enumeration and the processing functions corresponding to the message enumeration are in one-to-one correspondence.

Register message during initialization

During initialization, load the enumeration and the corresponding Action.

private void SubscribeMessageReceiver()
{
    mMessageReceiver.Add(EnumMsg.SEND_PANO_PARAM, UpdatePano);
    mMessageReceiver.Add(EnumMsg.CMD_PANO_VIEW, ExecutePanoViewCommand);
    mMessageReceiver.Add(EnumMsg.CMD_PANO_LENGTH_MEASURE, ExecuteLengthMeasure);
    mMessageReceiver.Add(EnumMsg.CMD_PANO_AREA_MEASURE, ExecuteAreaMeasure);
    mMessageReceiver.Add(EnumMsg.CMD_PANO_QUICK_PICK, ExecuteQickPickCommand);
}

This completes the construction of the key-value pair object. Then you can refactor the swith...case code segment.

Modify switch...case code segment

Switch....case code before reconstruction

protected override void DefWndProc(ref Message m)
      {
          switch (m.Msg)
          {
              case ((int)API.WM_COPYDATA):
                  {
                      switch ((int)m.WParam)
                      {
                          case ((int)Procedure.OpenSkyline):
                                 m = OpenSkylineView(m);
                              break;
                          case ((int)Procedure.Measureare):
                               m = Measure(m);
                              break;
                          case ((int)Procedure.Measurelength):
                               m = Measure(m);
                              break;
                      }
                  }
                  break;
              default:
                  break;
          }
          base.DefWndProc(ref m);
      }

Code to find the corresponding processing method based on key-value pairs

protected override void DefWndProc(ref Message m)
{
    base.DefWndProc(ref m);
    if (m.Msg == (int)API.WM_COPYDATA)
    {
        EnumPanoMsg pEnumPanoMsg = (EnumPanoMsg)m.WParam;
        if (mMessageReceiver.Keys.Contains(pEnumPanoMsg))
        {
            mMessageReceiver[pEnumPanoMsg](m);
        }
    }
}

Search based on the key of the key-value pair. When a new case branch needs to be added, the original method requires changing the switch....case branch, but using the key-value pair method, only Just write a new processing method and add a new pair of key values ​​to the key value pair. The code is concise and beautiful, without a long list of boring cases.

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