C#•10mo ago

✅ How to automatically check for null?

I have following code:

public IActionResult Put(                                              
    Guid id,                                                           
    UpdateItemDto updateItemDto)                                       
{                                                                      
    var existingItem = Items                                           
        .FirstOrDefault(item => item.Id == id);                        
                                                                       
    var updatedItem = existingItem with                                
    {                                                                  
        Name = updateItemDto.Name,                                     
        Description = updateItemDto.Description,                       
        Price = updateItemDto.Price                                    
    };                                                                 
                                                                       
    var index = Items.FindIndex(existingItem => existingItem.Id == id);
    Items[index] = updatedItem;                                        
                                                                       
    return NoContent();                                                
}

public IActionResult Put(                                              
    Guid id,                                                           
    UpdateItemDto updateItemDto)                                       
{                                                                      
    var existingItem = Items                                           
        .FirstOrDefault(item => item.Id == id);                        
                                                                       
    var updatedItem = existingItem with                                
    {                                                                  
        Name = updateItemDto.Name,                                     
        Description = updateItemDto.Description,                       
        Price = updateItemDto.Price                                    
    };                                                                 
                                                                       
    var index = Items.FindIndex(existingItem => existingItem.Id == id);
    Items[index] = updatedItem;                                        
                                                                       
    return NoContent();                                                
}

existingItem can be null so I will have NRE in this line var updatedItem = existingItem with. yes, we can solve this issue by checking existingItem for null but I don't want to do this every time, code looks much better without any checks so how to avoid this?

9 Replies

ero•10mo ago

if it can be null, then you have to check for null there's just no way around that and what if it doesn't exist after all?

TOKYODRIFT!•10mo ago

it is bad Smadge

ero•10mo ago

how? you have to handle it separately anyway

if (existingItem is null)
    return NotFound();

if (existingItem is null)
    return NotFound();

TOKYODRIFT!•10mo ago

I know but.. it's a little bit annoying to do

Thinker•10mo ago

Check for null, there is literally no good reason not to How would you do this otherwise?

ero•10mo ago

you could do

if (Items.FirstOrDefault(item => item.Id == id) is not { } existingItem)
    return NotFound();

if (Items.FirstOrDefault(item => item.Id == id) is not { } existingItem)
    return NotFound();

i guess

TOKYODRIFT!•10mo ago

I want the null check to be done automatically or all errors to be logged automatically so that I don't have to do it all myself but this looks good

ero•10mo ago

there's no such thing as an "automatic null check" you could call only .First(), but that will throw a different exception if the item doesn't exist

TOKYODRIFT!•10mo ago

sigh.. okay, thanks for helping me

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✅ How to automatically check for null?