pragma warning restore 1591

Question

我从数据库中挑选名单，根据情况，每个名字在数据库中存在很多次，没关系。现在我已经用这些名称填充了DROPDOWNLIST，但在下拉列表中，每个名称都出现了几次：

enter image description here

但我想在DROPDOWN中显示每个名字一次。我使用了distict（）但没有工作。

使用MVC 3，Linq to SQL

控制器：

 namespace EmployeeAttendance_app.Controllers
{
    public class HomeController : Controller
    {
        EmployeeAtdDataContext DataContext = new EmployeeAtdDataContext();

        public ActionResult Index()
        {
            ViewBag.Message = "Precise Technology Consultants";

            //var EmployeeAtd = DataContext.GetAttendance_Sp();
            IEnumerable<GetAtdRecord_SpResult> EmployeeAtd = DataContext.GetAtdRecord_Sp(null).ToList();
            var names = (from n in DataContext.EmployeeAtds select n).Distinct();
            //ViewData["EmplID"] = new SelectList(names, "EmplID", "EmplName");
            return View(EmployeeAtd);

        }
        public ActionResult ddl() 
        {
            var names = (from n in DataContext.EmployeeAtds select n).Distinct();
            ViewData["EmplID"] = new SelectList(names, "EmplID", "EmplName");
            return View();
        }
        public ActionResult showDDL(string EmplID) 
        {
            ViewBag.EmplID = EmplID;
            return View();
        }

        public ActionResult About()
        {
            return View();
        }

查看：

@{
    ViewBag.Title = "ddl";
}

<h2>ddl</h2>

    @using (Html.BeginForm("showDDL", "Home", FormMethod.Get))
    {
        <fieldset>

                Employers 

                 @Html.DropDownList("EmplID", "Select Name")

            <p>

                <input type="submit" value="Submit" />

            </p>

        </fieldset>


    }

模型

amespace EmployeeAttendance_app.Models
{
    using System.Data.Linq;
    using System.Data.Linq.Mapping;
    using System.Data;
    using System.Collections.Generic;
    using System.Reflection;
    using System.Linq;
    using System.Linq.Expressions;
    using System.ComponentModel;
    using System;


    [global::System.Data.Linq.Mapping.DatabaseAttribute(Name="a1")]
    public partial class EmployeeAtdDataContext : System.Data.Linq.DataContext
    {

        private static System.Data.Linq.Mapping.MappingSource mappingSource = new AttributeMappingSource();

    #region Extensibility Method Definitions
    partial void OnCreated();
    #endregion

        public EmployeeAtdDataContext() : 
                base(global::System.Configuration.ConfigurationManager.ConnectionStrings["a1ConnectionString"].ConnectionString, mappingSource)
        {
            OnCreated();
        }

        public EmployeeAtdDataContext(string connection) : 
                base(connection, mappingSource)
        {
            OnCreated();
        }

        public EmployeeAtdDataContext(System.Data.IDbConnection connection) : 
                base(connection, mappingSource)
        {
            OnCreated();
        }

        public EmployeeAtdDataContext(string connection, System.Data.Linq.Mapping.MappingSource mappingSource) : 
                base(connection, mappingSource)
        {
            OnCreated();
        }

        public EmployeeAtdDataContext(System.Data.IDbConnection connection, System.Data.Linq.Mapping.MappingSource mappingSource) : 
                base(connection, mappingSource)
        {
            OnCreated();
        }

        public System.Data.Linq.Table<EmployeeAtd> EmployeeAtds
        {
            get
            {
                return this.GetTable<EmployeeAtd>();
            }
        }

        [global::System.Data.Linq.Mapping.FunctionAttribute(Name="dbo.GetAtdRecord_Sp")]
        public ISingleResult<GetAtdRecord_SpResult> GetAtdRecord_Sp([global::System.Data.Linq.Mapping.ParameterAttribute(Name="EmplID", DbType="Int")] System.Nullable<int> emplID)
        {
            IExecuteResult result = this.ExecuteMethodCall(this, ((MethodInfo)(MethodInfo.GetCurrentMethod())), emplID);
            return ((ISingleResult<GetAtdRecord_SpResult>)(result.ReturnValue));
        }
    }

    [global::System.Data.Linq.Mapping.TableAttribute(Name="dbo.V_EmployeeAtd")]
    public partial class EmployeeAtd
    {

        private string _EmplID;

        private string _EmplName;

        private string _RecDate;

        private string _RecTime;

        private string _DeptName;

        public EmployeeAtd()
        {
        }

        [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_EmplID", DbType="Char(8) NOT NULL", CanBeNull=false)]
        public string EmplID
        {
            get
            {
                return this._EmplID;
            }
            set
            {
                if ((this._EmplID != value))
                {
                    this._EmplID = value;
                }
            }
        }

        [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_EmplName", DbType="NVarChar(40) NOT NULL", CanBeNull=false)]
        public string EmplName
        {
            get
            {
                return this._EmplName;
            }
            set
            {
                if ((this._EmplName != value))
                {
                    this._EmplName = value;
                }
            }
        }

        [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_RecDate", DbType="Char(10)")]
        public string RecDate
        {
            get
            {
                return this._RecDate;
            }
            set
            {
                if ((this._RecDate != value))
                {
                    this._RecDate = value;
                }
            }
        }

        [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_RecTime", DbType="Char(5)")]
        public string RecTime
        {
            get
            {
                return this._RecTime;
            }
            set
            {
                if ((this._RecTime != value))
                {
                    this._RecTime = value;
                }
            }
        }

        [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_DeptName", DbType="NVarChar(50)")]
        public string DeptName
        {
            get
            {
                return this._DeptName;
            }
            set
            {
                if ((this._DeptName != value))
                {
                    this._DeptName = value;
                }
            }
        }
    }

    public partial class GetAtdRecord_SpResult
    {

        private string _EmplID;

        private string _EmplName;

        private string _InTime;

        private string _OutTime;

        private string _DateVisited;

        private string _TimeWorked;

        private string _OverTime;

        public GetAtdRecord_SpResult()
        {
        }

        [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_EmplID", DbType="Char(8) NOT NULL", CanBeNull=false)]
        public string EmplID
        {
            get
            {
                return this._EmplID;
            }
            set
            {
                if ((this._EmplID != value))
                {
                    this._EmplID = value;
                }
            }
        }

        [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_EmplName", DbType="NVarChar(40) NOT NULL", CanBeNull=false)]
        public string EmplName
        {
            get
            {
                return this._EmplName;
            }
            set
            {
                if ((this._EmplName != value))
                {
                    this._EmplName = value;
                }
            }
        }

        [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_InTime", DbType="Char(5)")]
        public string InTime
        {
            get
            {
                return this._InTime;
            }
            set
            {
                if ((this._InTime != value))
                {
                    this._InTime = value;
                }
            }
        }

        [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_OutTime", DbType="Char(5)")]
        public string OutTime
        {
            get
            {
                return this._OutTime;
            }
            set
            {
                if ((this._OutTime != value))
                {
                    this._OutTime = value;
                }
            }
        }

        [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_DateVisited", DbType="Char(10) NOT NULL", CanBeNull=false)]
        public string DateVisited
        {
            get
            {
                return this._DateVisited;
            }
            set
            {
                if ((this._DateVisited != value))
                {
                    this._DateVisited = value;
                }
            }
        }

        [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_TimeWorked", DbType="Char(5)")]
        public string TimeWorked
        {
            get
            {
                return this._TimeWorked;
            }
            set
            {
                if ((this._TimeWorked != value))
                {
                    this._TimeWorked = value;
                }
            }
        }

        [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_OverTime", DbType="VarChar(6)")]
        public string OverTime
        {
            get
            {
                return this._OverTime;
            }
            set
            {
                if ((this._OverTime != value))
                {
                    this._OverTime = value;
                }
            }
        }
    }
}

pragma warning restore 1591

Answer 1

您需要确保您的基础对象覆盖GetHashCode和Equals，以使其正常工作。

请参阅此处了解更多信息：

http://msdn.microsoft.com/en-us/library/ms173147(v=vs.80).aspx

例如，如果您有一个名为EmployeeAtd的对象，则需要实现上述两种方法，以便了解比较对象何时相等。

这是一个简单的示例，但如果它们具有匹配的EmplID，您可以认为EmployeeAtd个对象是相同的，例如，等于覆盖可以是：

public override bool Equals(object obj)
{
    if (obj == null) return false;

    if (this.GetType() != obj.GetType()) return false;

    EmployeeAtd emp = (EmployeeAtd) obj;     

    if (!Object.Equals(EmplID, emp.EmplID)) return false;

    return true;
}

如果您的EmplID是int，则可以按如下方式实现GetHashCode：

public override int GetHashCode ()
{
    return EmplID.GetHashCode();
}

这不是最佳做法，但还有很多关于如何做到这一点的其他问题。

What is the best way to implement this composite GetHashCode()

Why is it important to override GetHashCode when Equals method is overridden?

Answer 2

您可以安全地使用DISTINCT，我不确定您在哪里遇到问题。请按照这个例子。说我有这样一个数据库表 - enter image description here

然后我按照存储过程编写

USE [Sample]
GO

CREATE PROCEDURE GiveNames
AS
SELECT DISTINCT(Name) FROM [dbo].[SampleTable]
GO

然后我创建一个MVC项目并添加EDMX并以下列方式使用Controller中的内容 -

public class EdmxController : Controller
{
    //
    // GET: /Edmx/
    public ActionResult Index()
    {
        DDLModel model = new DDLModel();
        model.Items = new List<string>();

        using (var entities = new SampleEntities1())
        {
            model.Items = entities.GiveNames().ToList();

        }
        return View(model);
    }
}

public class DDLModel
{
    public List<String> Items { get; set; }
}

我的观点 -

@model MVC.Controllers.DDLModel

@{
    ViewBag.Title = "Index";
}

<h2>Index</h2>

<div>
    @Html.DropDownList("MyDDL",new SelectList(Model.Items), "--Choose any Item--") 
</div>

我的输出没有重复 -

enter image description here

Answer 3

我认为你在n上实现了distinct，它包含了class的所有属性。您只需要在必需的列上应用distinct。像

 var empList= DataContext.EmployeeAtds.Select(n => new
        {
            EmplID= n.EmplID,
            EmplName= n.EmplName
        }).Distinct().ToList();

OR

 var empList= (from n in DataContext.EmployeeAtds select new{ EmplID= n.EmplID,
            EmplName= n.EmplName}).Distinct();

下拉菜单会多次显示每条记录

pragma warning restore 1591

3 个答案: