我的代码有数百个重复相等检查的实例 - 我该如何简化呢？

Question

The problem looks like I've had about 500 files with if statements looking like the one I have below. How might I replace these if statements without manually overwriting them each by each?

The if statement below returns a null reference exception if _azon is null so that is the main reason behind the replacement of the if statements.

 string _azon;
 public string azon
 {
     get { return _azon; }
     set {
         if (((_azon == null) && (value != null)) || !_azon.Equals(value)) {
              _azon = value;
              NotifyPropertyChanged();
          }
      }
  }

Answer 1

Based on your question and the code snippet in one of your comments, my understanding is that you want to replace this:

if (((_azon == null) && (value != null)) || !_azon.Equals(value)) {

with this:

if ((_azon == null) && (value != null)) {

You can do that with the Capture groups and replacement patterns feature in VisualStudio. You need to capture your variable name and use a replacement pattern to substitute it in the replacement string. Capturing the variable name is easy enough using the \w character class.

So your search expression would be:

if \(\(\((\w+) == null\) && \(value != null\)\) \|\| !\w+\.Equals\(value\)\) {

and your replacement pattern would be:

if (($1 == null) && (value != null)) {

Note the (\w+) in the search expression captures your variable, and the $1 in the replacement pattern substitutes it into the replacement text.

I find this site very useful for creating and testing regular expressions: https://regex101.com/

To do multi-file replacement in VisualStudio 2022 , you bring up the search dialog with the menu using "Edit/Find and Replace/Replace in Files" or use the Ctrl+Shift+H hotkey. On that dialog, you need to check the "Use regular expressions" checkbox.

Answer 2

Assuming your NotifyPropertyChanged method is implemented something like this:

private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")  
{  
    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}  

You could write a function that looks something like:

private void SetIfNeeded<T>(T value, ref T prop, [CallerMemberName] string propertyName = "") where T: class, IEquatable<T>
{
    if ((prop == null && value != null) || !prop.Equals(value))
    {
        prop = value;
        NotifyPropertyChanged(propertyName);
    }
}

and then consume in within your property setters this way:

string _azon;
public string azon
{
    get { return _azon; }
    set {
            SetIfNeeded(value, ref _azon);
        }
    }
}