EDIT:
I just realized that SaveChangesAsync returning 0 doesn't mean that it failed, entity framework will always throw exception when something fails so the check if SaveChanges == 0 is redundant! Save changes should always return 1 in the example below, if something fails then exception will be thrown.
However there are cases when something else is used and it's not entity framework so is this question for.
Servers can fail, when putting all my data access code in controllers I can handle it this way:
[HttpPost]
public async Task<ActionResult<Item>> CreateAsync([FromBody] Item item)
{
await _dbContext.AddAsync(item);
if (await _dbContext.SaveChangesAsync() == 0)
{
return StatusCode(StatusCodes.Status500InternalServerError);
}
return CreatedAtAction(nameof(GetAsync), new { id = item.Id }, item);
}
How should I handle it when my data access is encapsulated in a service layer?
public class ItemsService
{
public async Task<Item> CreateAsync(Item item)
{
await _dbContext.AddAsync(item);
if (await _dbContext.SaveChangesAsync() == 0)
{
return null;
}
return item;
}
}
Then it would be used like that:
[HttpPost]
public async Task<ActionResult<Item>> CreateAsync([FromBody] Item item)
{
// model state validation skipped for the sake of simplicity,
// that would return BadRequest or some more valuable information
var item = await _itemsService.CreateAsync(item);
if (item == null)
{
return StatusCode(StatusCodes.Status500InternalServerError);
}
return CreatedAtAction(nameof(GetAsync), new { id = item.Id }, item);
}
Maybe this works for fine creating because there are only 2 status codes but let's consider updating where there can be more than 2 possible errors like:
- Not found (404)
- Internal server error(500)
- Ok (200)
Code without services:
[HttpPut("{id}")]
public async Task<ActionResult<Item>> UpdateAsync(int id, [FromBody] Item itemToUpdate)
{
var item = await _dbContext.Items.FindAsync(id);
if (item == null)
{
return NotFound();
}
// update item with itemToUpdate
//...
await _dbContext.Update(item);
if (await _dbContext.SaveChangesAsync() == 0)
{
return StatusCode(StatusCodes.Status500InternalServerError);
}
return item;
}
Now with services this can't be properly handled:
public class ItemsService
{
public async Task<Item> UpdateAsync(Item updateItem)
{
var item = await _dbContext.Items.FindAsync(id);
if (item == null)
{
return null;
}
//change some properties and update
//...
_dbContext.Items.Update(item);
if (await _dbContext.SaveChangesAsync() == 0)
{
// what now?
}
return item;
}
}
because it always returns null and there's no way to tell if the item was not found or the saving failed.
How can I handle it properly?
Note: I didn't add DTO or anything like that to keep this example simple.
