我目前正在将控制台应用程序转换为 Windows 窗体应用程序。 幸运的是，我最初设计的应用程序是为了将来与 GUI 一起使用，因此不需要更改太多代码。
我有一个 UserCollection 类，它本身包含一个 User/Member 类型的 List<>(Member 派生自 User)。
我想做的是将 UserCollection List<> 中的每个项目添加到 ListView，这样我就可以看到每个条目并垂直列出多个条目。
我首先尝试自己实现这一点:
private void UpdatePeopleListings()
{
foreach (User person in newCollection)
{
listViewPeople.Items.Add(person.ToString());
}
}
其中 newCollection 是从主窗口窗体中的 UserCollection 类创建的新对象。
我收到错误:
foreach statement cannot operate on variables of type 'Collection.UserCollection' because 'Collection.UserCollection' does not contain a public definition for 'GetEnumerator'
然后我尝试做一个小的解决方法，所以在我的 UserCollection 中我创建了以下方法:
public User ReturnUser()
{
foreach (User person in _userCollection)
{
return person;
}
return null;
}
(_userCollection 是 UserCollection.cs 中的用户/成员列表<>)
然后像这样使用它:
private void UpdatePeopleListings()
{
listViewPeople.Items.Add(newCollection.ReturnUser().ToString());
}
尽管这确实使用条目填充了 ListView，但它仅填充了第一个条目。 如果我要向 newCollection 添加多个用户/成员，那么它只会重复第一个条目。
我如何正确地使用集合中的所有对象填充 ListView 以及如何防止它仅重复一个对象。
UserCollecton.cs
///////////////////////////////////////////////////////////
// UserCollection.cs
// Implementation of the Class UserCollection
// Generated by Enterprise Architect
// Created on: 22-Oct-2009 22:40:30
///////////////////////////////////////////////////////////
#region Using Statements
using System;
using System.Collections.Generic;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
using System.IO;
#endregion
namespace Collection
{
//Allows the class to be saved
[Serializable()]
public class UserCollection
{
#region Fields
//Declares a list of type User (Which also holds derived Member objects)
private List<User> _userCollection = new List<User>();
//Holds number of members
int nMember = 0;
//Holds number of users
int nUser = 0;
#endregion
#region Add Operations
/// <summary>
/// Adds a new user
/// </summary>
/// <param name="user"></param>
public void AddUser(User user)
{
//Adds the user given in the operation parameters to the collection
_userCollection.Add(user);
nUser++;
//Sorts the collection using the CompareTo() specified in the User class.
_userCollection.Sort();
//Console.WriteLine used for testing purposes
//Console.WriteLine("added");
}
///<summary>
///Adds a new Member
///</summary>
/// <param name="member"></param>
public void AddMember(Member member)
{
//Adds the member given in the operation parameters to the collection
_userCollection.Add(member);
nMember++;
//Sorts the collection using the CompareTo() specified in the User class.
_userCollection.Sort();
//Console.WriteLine used for testing purposes
//Console.WriteLine("added");
}
#endregion
#region Removal Operations
///<summary>
///Removes a user based on FirstName,LastName and PostCode
///</summary>
/// <param name="person"></param>
public void RemoveUser(User person)
{
//Only search collection for users if there is data in it
if (_userCollection.Count > 0)
{
//Create a temp list for any matched found
List<User> tempList = new List<User>();
foreach (User u in _userCollection)
{
//If the details stored in the collection match the details given in the search
if (u.FName == person.FName && u.LName == person.LName && u.PostCode == person.PostCode)
{
//Add any matches to the temp list
tempList.Add(u);
}
else
{
throw new ArgumentException("User not found");
}
}
//Delete any matches
foreach (User u in tempList)
{
_userCollection.Remove(u);
//Decrement user count
nUser--;
}
}
else
{
throw new AccessViolationException("No data in collection");
}
}
/// <summary>
/// Removes a user using Membership number
/// </summary>
/// <param name="number"></param>
public void RemoveMember(int number)
{
//Create a temp list of type Member
Member temp = new Member();
//Use the temp list to compare types and store all objects of type member
//found in the collection to it.
List<User> Mems = _userCollection.FindAll(delegate(User u)
{ return u.GetType() == temp.GetType(); });
//Delete any matches
foreach (Member m in Mems)
{
if (m.mNum == number)
{
_userCollection.Remove(m);
//Decrement member count
nMember--;
}
else
{
throw new ArgumentException("Member not found");
}
}
}
#endregion
#region Search Operations
///<summary>
///Returns member by Membership number
/// </summary>
///
/// <param name="_mNumber"></param>
public Member FindByMNo(int number)
{
//Create a temp list of type Member
Member temp = new Member();
//Use the temp list to compare types and store all objects of type member
//found in the collection to it.
List<User> Mems = _userCollection.FindAll(delegate(User u)
{ return u.GetType() == temp.GetType(); });
//Return any matches found
foreach (Member i in Mems)
{
if (i.mNum == number)
{
return i;
}
}
throw new ArgumentException("Member not found");
}
///<summary>
///Returns a list of Users matching details given
///</summary>
///
/// <param name="_fName"></param>
/// <param name="_lName"></param>
public List<User> FindByName(User person)
{
//Create a temp list to store any matches
List<User> temp = new List<User>();
//Add matches found to the temp list
foreach (User u in _userCollection)
{
if (u.LName == person.LName)
{
temp.Add(u);
}
}
if (temp.Count > 0)
{
//Return the list that holds any matches
return temp;
}
throw new ArgumentException("User not found");
}
public User ReturnUser()
{
foreach (User person in _userCollection)
{
return person;
}
return null;
}
#endregion
#region Edit Operations
///<summary>
///Edits a members membership expiry
///</summary>
///
/// <param name="member"></param>
public void EditMemStatus(int member, DateTime newDate)
{
//Create a temp list of type Member
Member temp = new Member();
//Use the temp list to compare types and store all objects of type member
//found in the collection to it.
List<User> Mems = _userCollection.FindAll(delegate(User u)
{ return u.GetType() == temp.GetType(); });
//Search for the member that matches the number given in the parameter
foreach (Member m in Mems)
{
if (m.mNum == member)
{
//Replace the match with the new expiry
m.mExp = newDate;
}
else
{
throw new ArgumentException("Date cannot be changed");
}
}
}
#endregion
#region I/O Operations
public bool SaveData()
{
try
{
//Open the stream using the Data.txt file
using (Stream stream = File.Open("Data.txt", FileMode.Create))
{
//Create a new formatter
BinaryFormatter bin = new BinaryFormatter();
//Copy data in collection to the file specified earlier
bin.Serialize(stream, _userCollection);
bin.Serialize(stream, nMember);
bin.Serialize(stream, nUser);
//Close stream to release any resources used
stream.Close();
}
return true;
}
catch (IOException ex)
{
throw new ArgumentException(ex.ToString());
}
}
public bool LoadData()
{
//Check if file exsists, otherwise skip
if (File.Exists("Data.txt"))
{
try
{
using (Stream stream = File.Open("Data.txt", FileMode.Open))
{
BinaryFormatter bin = new BinaryFormatter();
//Copy data back into collection fields
_userCollection = (List<User>)bin.Deserialize(stream);
nMember = (int)bin.Deserialize(stream);
nUser = (int)bin.Deserialize(stream);
stream.Close();
//Sort data to ensure it is ordered correctly after being loaded
_userCollection.Sort();
return true;
}
}
catch (IOException ex)
{
throw new ArgumentException(ex.ToString());
}
}
else
{
//Console.WriteLine present for testing purposes
Console.WriteLine("\nLoad failed, Data.txt not found");
return false;
}
}
#endregion
#region Properties
//Gets amount of Members in collection
public int GetNMember
{
get
{
return nMember;
}
}
//Gets amount of Users in collectioj
public int GetNUser
{
get
{
return nUser;
}
}
#endregion
}//end UserCollection
}
忽略任何随机的控制台内容，我还没有完成清理工作。
最佳答案
foreach 不起作用，因为您的 UserCollection 类没有实现 IEnumerable 接口(interface)。
ListItems 不是您所期望的，因为您不了解 ListView/ListViewItems 的工作原理。 ListView 由 ListViewItem 组成，ListViewItem 可以由 SubItem 组成(仅当 ListView 的 View 样式设置为“report”时才显示)。
当您使用正在使用的方法添加 ListViewItem 时，仅定义 ListViewItem 的“标题”。 这意味着，您必须使用 Add 方法的另一个重载；该方法采用 ListViewItem 对象作为参数。 然后，您可以这样做:
ListViewItem item = new ListViewItem();
item.Text = "bar";
item.SubItems.Add ("foo");
item.SubItems.Add ("foo2");
myListView.Items.Add (item);
关于仅将一项添加到您的列表中的问题: - 您只添加一项...更具体地说，您添加集合本身，而不是为集合中的每个对象创建一个 ListViewItem。
所以你要做的是:
- 迭代您的列表(使用 foreach (意味着您必须在集合类上实现 IEnumerable)，或使用 for 循环(但您必须确保可以使用索引器访问集合的内容实例))
- 为列表中存在的每个对象创建一个 ListViewItem。
我想知道您为什么首先创建自定义 UserCollection。我看到您已经实现了一些特定的功能，但是......我认为有更好的解决方案。 尽管如此，您应该为该类实现 IEnumerable 接口(interface)、IList 接口(interface)等。通过这样做，您的类将成为“真正的集合”，然后您可以像任何其他集合类一样使用它。 (使用 foreach 或使用 for 循环等进行迭代。)
关于.net - 使用 List<> 中的对象填充 ListView，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/1810842/