[英]Select distinct from List<t> ignoring one element
I have a List of custom a datatype, simplified example ( myMovies
): 我有一个自定义数据类型列表,简化示例(
myMovies
):
public class Movie
{
public Int32 TVIndex;
public string MovieName;
public string MovieRating;
public string MovieRuntime;
public List<Actor> MovieActors;
public List<MovieArt> MovieImages;
}
public class Actor
{
public string ActorName;
public string ActorRole;
}
public class MovieArt
{
public string ImagePath;
}
List<Movie> myMovies = new List<Movie>();
Now I am trying to remove all duplicates from myMovies
but ignoring TVIndex
. 现在我试图从
myMovies
删除所有重复但忽略TVIndex
。
I have tried looking at 我试过看
List<Movie> myDistinctMovies = myMovies.Distinct().ToList();
But cannot figure out how to ignore TvIndex
. 但无法弄清楚如何忽略
TvIndex
。 Is this possible? 这可能吗?
Based on @Grundy's answer, including implementation: 基于@Grundy的回答,包括实施:
public class MovieEqualityComparer : IEqualityComparer<Movie>
{
public bool Equals(Movie x, Movie y)
{
if ( x == null )
return y == null;
if ( y == null )
return x == null;
if ( object.ReferenceEquals(x, y) )
return true;
if ( !string.Equals(x.MovieName, y.MovieName) )
return false;
if ( !string.Equals(x.MovieRating, y.MovieRating) )
return false;
if ( !string.Equals(x.MovieRuntime, y.MovieRuntime) )
return false;
if ( !Enumerable.SequenceEqual(x.MovieActors, y.MovieActors) )
return false;
if ( !Enumerable.SequenceEqual(x.MovieImages, y.MovieImages) )
return false;
return true;
}
public int GetHashCode(Movie obj)
{
if ( obj == null )
throw new ArgumentNullException();
unchecked
{
int hash = 17;
hash = hash * 31 + ((obj.MovieName == null) ? 0 : obj.MovieName.GetHashCode());
hash = hash * 31 + ((obj.MovieRating == null) ? 0 : obj.MovieRating.GetHashCode());
hash = hash * 31 + ((obj.MovieRuntime == null) ? 0 : obj.MovieRuntime.GetHashCode());
if ( obj.MovieActors != null )
{
foreach ( var actor in obj.MovieActors )
hash = hash * 31 + ((actor == null) ? 0 : actor.GetHashCode());
}
if ( obj.MovieImages != null )
{
foreach ( var image in obj.MovieImages )
hash = hash * 31 + ((image == null) ? 0 : image.GetHashCode());
}
return hash;
}
}
}
Usage is the same: 用法是一样的:
List<Movie> myMovies = new List<Movie>
{
// ...
};
List<Movie> myDistinctMovies = myMovies.Distinct(new MovieEqualityComparer()).ToList();
EDIT 编辑
As pointed out by @Tim, you have to do something quite similar for your other custom types if you want to compare by anything other than reference equality. 正如@Tim所指出的,如果你想通过除引用相等之外的任何东西进行比较,你必须为你的其他自定义类型做一些非常类似的事情。
public class Actor : IEquatable<Actor>
{
public string ActorName;
public string ActorRole;
public override bool Equals(object obj)
{
return this.Equals(obj as Actor);
}
public bool Equals(Actor other)
{
if ( other == null )
return false;
if ( object.ReferenceEquals(this, other) )
return true;
if ( !string.Equals(this.ActorName, other.ActorName) )
return false;
if ( !string.Equals(this.ActorRole, other.ActorRole) )
return false;
return true;
}
public override int GetHashCode()
{
unchecked
{
int hash = 17;
hash = hash * 31 + ((ActorName == null) ? 0 : ActorName.GetHashCode());
hash = hash * 31 + ((ActorRole == null) ? 0 : ActorRole.GetHashCode());
return hash;
}
}
}
public class MovieArt : IEquatable<MovieArt>
{
public string ImagePath;
public override bool Equals(object obj)
{
return this.Equals(obj as MovieArt);
}
public bool Equals(MovieArt other)
{
if ( other == null )
return false;
if ( object.ReferenceEquals(this, other) )
return true;
if ( !string.Equals(this.ImagePath, other.ImagePath) )
return false;
return true;
}
public override int GetHashCode()
{
unchecked
{
int hash = 17;
hash = hash * 31 + ((ImagePath == null) ? 0 : ImagePath.GetHashCode());
return hash;
}
}
}
you can use Distinct with EqualityComparer something like this 你可以使用Distinct with EqualityComparer这样的东西
public class MoviesEqualityComparer : IEqualityComparer<Movie>
{
public bool Equals(Movie x, Movie y)
{
return ..../* check all needed fields */
}
public int GetHashCode(Movie obj)
{
return .... /* get hashcode for movie objec*/
}
}
and use it like 并使用它
List<Movie> myDistinctMovies = myMovies.Distinct(new MoviesEqualityComparer()).ToList();
you could use a LINQ Query may be ... 你可以使用LINQ查询可能...
List<Movie> myDistinctMovies = (myMovies .GroupBy(p =>p.MovieName,
p =>p.MovieRating,p=>p.MovieRuntime)
.Select(g => g.First())
.ToList());
Thanks.. 谢谢..
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