如何使 C# api 中所需的参数

Question

so for now it will match both of the actions by the route api/comments, I want the second one to be api/comments?blogId=1, but I don't want it to be api/comments/{blogId}.

//Get api/comments
[HttpGet]
[Route("/")]
public async Task<IActionResult> GetAll()
{
    var comments = await _context.Comments.ToListAsync();

    if(comments != null)
        return Ok(new { status = 200, comments });
    
    return NotFound();
}

//Get api/comments?blogId=1
[HttpGet]
public async Task<IActionResult> GetCommentsBy(int blogId)
{
    var allComments = await _context.Comments.ToListAsync();          

    if (allComments != null)
    {
        var commentsByBlogId = allComments.Where(c => c.BlogId == blogId);

        return Ok(new { status = 200, comments = commentsByBlogId });
    }         

    return NotFound();
}

Answer 1

Routes are unique by looking at there themplate. Even if you're using blogId as query parameter, the two actions are using the same route template which is this api/comments .

To do what you're trying to do is to using only have one action that will return result when you send a blogId or not.

So just add one action Get and the logic should look like below:

[HttpGet]
public async Task<IActionResult> GetComments(int? blogId /* blogId i nullable so it is not required */)
{
    // Gets the comments query but don't execute it yet. So no call to ToListAsync() here.
    var commentsQuery = _context.Comments;

    if  (blogId.HasValue)
    {
        // When you've a blogId set in the query then add a filter to the query.
        commentsQuery = commentsQuery.Where(c => c.BlogId == blogId);
    }

    var comments = await commentsQuery.ToListAsync();       

    // When the list is empty just send it as it is. the caller should be able to handle the case where the comments list is empty and status code is 200
    // You also don't need to set the status code in your responde body. The caller should be able to get the response status first before checking the response body.
    return Ok(comments);
}