Question

我试图从表中选择并返回某些列，查询忽略选择并返回相关表中相关字段之外的所有列。如何只返回选定的列？

这是我的API Controller，

    [Produces("application/json")]
    [Route("api/Common")]
public class CommonController : Controller
{
    private readonly ArtCoreDbContext _context;

    public CommonController(ArtCoreDbContext context)
    {
        _context = context;
    }

    [HttpGet]
    public IEnumerable<IdState> GetState()
    {
        return _context.IdState;
    }

    [HttpGet("{id}")]
    public async Task<IActionResult> GetState([FromRoute] int id)
    {
        var  L2EQuery = await (from i in _context.IdState
                                      select new { Id = i.StaeId, i.text }).ToListAsync();

        return Ok(L2EQuery);
    }
}

更新

这是模型，

public class IdState
        {
            [DatabaseGenerated(DatabaseGeneratedOption.Identity), Key]
            public int StaeId { set; get; }
            public int CouyId { set; get; }
            [Display(Name = "State"), Required]
            public string text { set; get; }
            public ICollection<PatReg> State { get; set; }
            public ICollection<IdCity> TblIdCity { get; set; }

        }

，输出为，

[{
    "staeId": 1,
    "couyId": 2,
    "text": "California",
    "state": null,
    "tblIdCity": null
}, {
    "staeId": 2,
    "couyId": 2,
    "text": "WA",
    "state": null,
    "tblIdCity": null
}, {
    "staeId": 3,
    "couyId": 1,
    "text": "Ajloun",
    "state": null,
    "tblIdCity": null
}, {
    "staeId": 4,
    "couyId": 1,
    "text": "Amman",
    "state": null,
    "tblIdCity": null
}]

ajax致电

@section Scripts {
    @{await Html.RenderPartialAsync("_ValidationScriptsPartial");}
    <script src="~/ArtCoreScripts/Pages/ClinicCore/PatientRegistration.js"></script>
    <script>
        $(function () {
            $.ajax({
                type: "Get",
                url: "/api/Common",
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: function (response) {
                    console.log(response);
                },
                failure: function (response) {
                    alert(response.responseText);
                },
                error: function (response) {
                    alert(response.responseText);
                }
            });
        });
    </script>}

使用LINQPad 5我只获取所选列

Answer 1

您的C＃代码没有问题，但是JavaScript。

您没有在控制器中指定操作，因此默认为无参数HttpGet启用的操作，该操作不会投影任何字段。所以问题出在你的AJAX调用中。像这样纠正：

$.ajax({
    type: "Get",
    // Pay attention on the next line !
    url: "/api/Common/123",
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: function (response) {
        console.log(response);
    },
    failure: function (response) {
        alert(response.responseText);
    },
    error: function (response) {
        alert(response.responseText);
    }
});

＆＃34; 123＆＃34;只是一个例子，但我可以看到，目前它并不重要，因为你不能过滤LINQ中的任何东西。但是，您必须在URL中指定它，以便可以将其解析为正确的方法。

Answer 2

我认为，你调用方法public IEnumerable<IdState> GetState()并返回整个表格。

也许，您需要致电Task<IActionResult> GetState([FromRoute] int id)

问题在这里： url: "/api/Common",你调用了错误的方法，添加参数：

url: "/api/Common/123",

或者也许：

    $(function () {
        $.ajax({
            type: "Get",
            url: "/api/Common",
            data: {id: 123},
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            success: function (response) {
                console.log(response);
            },
            failure: function (response) {
                alert(response.responseText);
            },
            error: function (response) {
                alert(response.responseText);
            }
        });
    });

Answer 3

你能试试吗

 public class CommonController : Controller
    {

        private readonly ArtCoreDbContext _context;

        public CommonController(ArtCoreDbContext context)
        {
            _context = context;
        }

        [HttpGet]
        public IEnumerable<IdState> GetState()
        {

            return _context.IdState;
        }
        [HttpGet("{id}")]
        public async Task<IActionResult> GetState([FromRoute] int id)
        {
            var  L2EQuery = await (from i in _context.IdState
                                    where i.test.equals("abc")
                                      select new { Id = i.StaeId, text= i.text }).ToListAsync();

            return Ok(L2EQuery);
        }
    }

LINQ Select语法返回所有列而不是选定列

3 个答案: