c# – 从列表中返回匹配>
发布时间：2020-12-16 01:33:26 所属栏目：百科 来源：网络整理
导读：我目前有一个类使用带有List的KeyValuePair来存储Key = track,Value = artist格式的轨道集合. 我正在尝试提供一种搜索特定曲目的方法,如果有任何匹配,则返回整个匹配的CD. 这是我到目前为止的尝试： public CompilationCD FindTrackInComCD(string track){ C
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我目前有一个类使用带有List的KeyValuePair来存储Key = track,Value = artist格式的轨道集合.
我正在尝试提供一种搜索特定曲目的方法,如果有任何匹配,则返回整个匹配的CD. 这是我到目前为止的尝试： public CompilationCD FindTrackInComCD(string track)
{
CompilationCD temp = new CompilationCD();
List<CD> tempComCols = _cdCollection.FindAll(delegate(CD cd)
{ return cd.GetType() == temp.GetType(); });
foreach (KeyValuePair<string,string> comCD in tempComCols)
{
if (comCD.Key.Contains(track))
{
return comCD;
}
}
throw new ArgumentException("No matches found");
}
我有一个CD类型的CD集合(List< CD>)因此我创建了一个新的List<>通过将它与临时列表进行比较来获得适当的类型. 编译时我收到以下错误： Cannot convert type 'CDCollection.CD' to System.Collections.Generic.KeyValuePair<string,string>' Cannot implicitly convert type 'System.Collections.Generic.KeyValuePair<string,string>' (CDCollection是我的项目命名空间,CD / CompilationCD是类) 对不起,这似乎与我之前提出过的问题类似.我尝试使用之前给出的方法,但我有点难过;我没有使用List<>或KeyValuePair经常. 这是CD类： using System; 使用System.Collections; 命名空间CDCollection #region Constructors
public CD()
{
_artist = "";
_album = "";
_track = null;
}
public CD(string albumName)
{
_album = albumName;
}
public CD(string artistName,string albumName)
{
_artist = artistName;
_album = albumName;
}
#endregion
#region Properties
/// <summary>
/// Get/Set Artist Name
/// </summary>
public virtual string Artist
{
get
{
return _artist;
}
set
{
value = _artist;
}
}
/// <summary>
/// Get/Set Album
/// </summary>
public string Album
{
get
{
return _album;
}
set
{
value = _album;
}
}
/// <summary>
/// Get/Set Track Name
/// </summary>
public virtual List<string> Track
{
get
{
return _track;
}
set
{
value = _track;
}
}
#endregion
#region ToString()
/// <summary>
/// Custom ToString() Method
/// </summary>
/// <returns></returns>
public override string ToString()
{
//Create new StringBuilder object
StringBuilder sb = new StringBuilder();
sb.Append("Artist Name");
//Display error if Artist is not available
if (_artist == null || _artist == "")
{
sb.Append("nNo Artist Entered");
}
else
{
sb.Append("n" + this._artist);
}
sb.Append("n");
sb.Append("nAlbum Name");
//Display error if Album is not available
if (_album == null || _album == "")
{
sb.Append("nNo Album Entered");
}
else
{
sb.Append("n" + this._album);
}
sb.Append("n");
sb.Append("nTrack Name");
sb.Append("n");
//Iterate through all tracks stored in list
foreach (string trackName in _track)
{
//Print each artist
sb.Append("n" + trackName);
}
sb.Append("nEnd of CD Record.........");
return sb.ToString();
}
#endregion
}
} 这是CompilationCD类： using System; 使用System.Collections.Generic; 命名空间CDCollection private readonly string _artist;
private readonly string _album;
private List<KeyValuePair<string,string>> _tracks = new List<KeyValuePair<string,string>>();
//List<KeyValuePair> Reference.
//http://msdn.microsoft.com/en-us/library/6sh2ey19(VS.85).aspx
#endregion
#region Constructors
public CompilationCD()
{
_album = "";
_artist = "Various Artists";
}
public CompilationCD(string albumName):base(albumName)
{
_album = albumName;
_artist = "Various Artists";
}
#endregion
public void AddTracks(string track,string artist)
{
_tracks.Add(new KeyValuePair<string,string>(track,artist));
}
#region Properties
public override string Artist
{
get
{
return this._artist;
}
}
public new List<KeyValuePair<string,string>> Track
{
get
{
return _tracks;
}
set
{
_tracks = value;
}
}
#endregion
#region ToString()
//TEST
public override string ToString()
{
//Create new StringBuilder object
StringBuilder sb = new StringBuilder();
sb.Append("Artist Name");
//Display error if Artist is not available
if (_artist == null || _artist == "")
{
sb.Append("nNo Artist Entered");
}
else
{
sb.Append("n" + this._artist);
}
sb.Append("n");
sb.Append("nAlbum Name");
//Display error if Album is not available
if (base.Album == null || base.Album == "")
{
sb.Append("nNo Album Entered");
}
else
{
sb.Append("n" + base.Album);
}
sb.Append("n");
sb.Append("nTrack Name");
sb.Append("n");
////Iterate through all tracks stored in list
//foreach (string trackName in base.Track)
//{
// //Print each artist
// sb.Append("n" + trackName);
//}
for(int i = 0; i <= _tracks.Count; i++)
{
string track = _tracks[i].Key;
string artist = _tracks[i].Value;
sb.Append("nTrack");
sb.Append(track);
sb.Append("nArtist");
sb.Append(artist);
}
sb.Append("nEnd of Compilation CD Record.........");
return sb.ToString();
}
#endregion
}
} 我有严格的规则,这意味着我必须从CD继承以创建我的CompilationCD以及使用List>对于我的曲目集,它需要同时拥有曲目和艺术家.疯了我知道= / 此外,我必须将所有类型的CD存储在CD(List)类型的列表中. 解决方法
问题出在你的foreach循环中. tempComCols是List< CD>,但comCD是KeyValuePair< string,string>.因此,您的循环导致无效的类型转换.
不幸的是,由于我们不知道CD类(接口？)是什么样的,我不能建议修复它的属性. 编辑：以下可能是您的方法的更好版本(但是,我没有正确调试它)： public CompilationCD FindTrackInComCD(string track)
{
CompilationCD temp = new CompilationCD();
temp = _cdCollection.Where(cd => cd is CompilationCD)
.Cast<CompilationCD>()
.Where(com_cd => com_cd.Tracks.ContainsKey(track))
.FirstOrDefault();
if (temp != null)
return temp;
else throw new ArgumentException("No matches found");
}
你不能将CompilationCD转换为KeyValuePair< string,string>,所以我们只是直接使用CompilationCD类.我们可以将搜索轨道列表的责任转移到IEnumerable< T> System.Linq提供的扩展方法,使这个方法非常简单. （编辑：李大同） 【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容! |