I have two methods:

static public async Task Delete( Guid id, string path, ViewModelCollection<ProfileData> collection )       
{                                                                                                          
    var jsonText = await File.ReadAllTextAsync( path );                                                    
    var jsonList = JsonConvert.DeserializeObject<List<ProfileData>>( jsonText );                           
    if ( jsonList != null && jsonList.Any() )                                                              
    {                                                                                                      
        var itemToDelete = jsonList                                                                        
            .FirstOrDefault( x => x.Id == id );                                                            
                                                                                                           
        if ( itemToDelete != null )                                                                        
        {                                                                                                  
            jsonList.Remove( itemToDelete );                                                               
        }                                                                                                  
    }                                                                                                      
                                                                                                           
    var output = JsonSerializer.Serialize( jsonList );                                                     
    await File.WriteAllTextAsync( path, output );                                                          
                                                                                                           
    var item = collection.FirstOrDefault( x => x.Id == id );                                               
    if ( item != null ) collection.Remove( item );                                                         
}                                                                                                          
                                                                                                           
static public async Task Delete( Guid id, string path, ViewModelCollection<SubscriptionData> collection )  
{                                                                                                          
    var jsonText = await File.ReadAllTextAsync( path );                                                    
    var jsonList = JsonConvert.DeserializeObject<List<SubscriptionData>>( jsonText );                      
    if ( jsonList != null && jsonList.Any() )                                                              
    {                                                                                                      
        var itemToDelete = jsonList                                                                        
            .FirstOrDefault( x => x.Id == id );                                                            
                                                                                                           
        if ( itemToDelete != null )                                                                        
        {                                                                                                  
            jsonList.Remove( itemToDelete );                                                               
        }                                                                                                  
    }                                                                                                      
                                                                                                           
    var output = JsonSerializer.Serialize( jsonList );                                                     
    await File.WriteAllTextAsync( path, output );                                                          
                                                                                                           
    var item = collection.FirstOrDefault( x => x.Id == id );                                               
    if ( item != null ) collection.Remove( item );                                                         
}                       

The problem, I think, is immediately visible - ProfileData simply changes to SubscriptionData. Question: how to avoid this?

I wanna have this:

static public async Task Delete<T>(...){... var itemToDelete = jsonList.FirstOrDefault(x => x.Id == id ...)          

The problem is x.Id of unknown class

CodePudding user response：

The problem is x.Id of unknown class

Declare an interface IHasId which defines your Id property, and make sure that both ProfileData and SubscriptionData implement that interface.

You can then constrain your generic method declaration as follows:

static public async Task Delete<T>(...) where T : IHasId
{ ... }

(Obviously, if you already have a base class for ProfileData and SubscriptionData which defines the Id property, you can just constrain your generic parameter to that base class.)