序列包含多个元素
本文关键字：元素 包含多 | 更新日期: 2023-09-27 18:13:58
我得到这个错误:
System.InvalidOperationException: Sequence contains more than one element
at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source)
at System.Data.Entity.Core.Objects.ELinq.ObjectQueryProvider.<GetElementFunction>b__2[TResult](IEnumerable`1 sequence)
at System.Data.Entity.Core.Objects.ELinq.ObjectQueryProvider.ExecuteSingle[TResult](IEnumerable`1 query, Expression queryRoot)
at System.Data.Entity.Core.Objects.ELinq.ObjectQueryProvider.System.Linq.IQueryProvider.Execute[TResult](Expression expression)
at System.Data.Entity.Internal.Linq.DbQueryProvider.Execute[TResult](Expression expression)
at System.Linq.Queryable.SingleOrDefault[TSource](IQueryable`1 source, Expression`1 predicate)
at System.Data.Entity.Migrations.DbSetMigrationsExtensions.AddOrUpdate[TEntity](DbSet`1 set, IEnumerable`1 identifyingProperties, InternalSet`1 internalSet, TEntity[] entities)
at System.Data.Entity.Migrations.DbSetMigrationsExtensions.AddOrUpdate[TEntity](IDbSet`1 set, Expression`1 identifierExpression, TEntity[] entities)
at ArtistDatabase.Migrations.Configuration.Seed(ArtistDBContext context) in C:'Users'Will'Desktop'ArtistDatabase'ArtistDatabase'Migrations'Configuration.cs:line 196
at System.Data.Entity.Migrations.DbMigrationsConfiguration`1.OnSeed(DbContext context)
at System.Data.Entity.Migrations.DbMigrator.SeedDatabase()
at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.SeedDatabase()
at System.Data.Entity.Migrations.DbMigrator.Upgrade(IEnumerable`1 pendingMigrations, String targetMigrationId, String lastMigrationId)
at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.Upgrade(IEnumerable`1 pendingMigrations, String targetMigrationId, String lastMigrationId)
at System.Data.Entity.Migrations.DbMigrator.UpdateInternal(String targetMigration)
at System.Data.Entity.Migrations.DbMigrator.<>c__DisplayClassc.<Update>b__b()
at System.Data.Entity.Migrations.DbMigrator.EnsureDatabaseExists(Action mustSucceedToKeepDatabase)
at System.Data.Entity.Migrations.Infrastructure.MigratorBase.EnsureDatabaseExists(Action mustSucceedToKeepDatabase)
at System.Data.Entity.Migrations.DbMigrator.Update(String targetMigration)
at System.Data.Entity.Migrations.Infrastructure.MigratorBase.Update(String targetMigration)
at System.Data.Entity.Migrations.Design.ToolingFacade.UpdateRunner.Run()
at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
at System.Data.Entity.Migrations.Design.ToolingFacade.Run(BaseRunner runner)
at System.Data.Entity.Migrations.Design.ToolingFacade.Update(String targetMigration, Boolean force)
at System.Data.Entity.Migrations.UpdateDatabaseCommand.<>c__DisplayClass2.<.ctor>b__0()
at System.Data.Entity.Migrations.MigrationsDomainCommand.Execute(Action command)
Sequence contains more than one element
这是我的两个情态，我是新的，但我不确定这是因为他们都有"名称"answers"图片"，或者因为"ArtistID"在艺术模态，虽然它应该是一个外键。
艺术家public class Artist
{
public int ArtistID { get; set; }
//----------------------------------------------------------------------------------------------
[Required,StringLength(60, MinimumLength = 3), Display(Name = "Artist")]
public string Name { get; set; }
//----------------------------------------------------------------------------------------------
[DataType(DataType.ImageUrl)]
public string Picture { get; set; }
//----------------------------------------------------------------------------------------------
[System.ComponentModel.DataAnnotations.Schema.Column(TypeName = "datetime2")]
[Display(Name = "Date of Birth"),DataType(DataType.Date),DisplayFormat(DataFormatString = "{0:dd-MM-yyyy}", ApplyFormatInEditMode = true)]
public DateTime BirthDate { get; set; }
//----------------------------------------------------------------------------------------------
[Required,StringLength(30)]
public string Nationality { get; set; }
//----------------------------------------------------------------------------------------------
[Display(Name = "Style/Movement")]
public string ArtStyle { get; set; }
//----------------------------------------------------------------------------------------------
[DataType(DataType.MultilineText)]
public string Info { get; set; }
//----------------------------------------------------------------------------------------------
[RegularExpression(@"^[A-Z]+[a-zA-Z''-''s]*$")]
[StringLength(5)]
public string Rating { get; set; }
//----------------------------------------------------------------------------------------------
[Display(Name = "Famous work: "),DataType(DataType.ImageUrl)]
public string Artwork1 { get; set; }
//----------------------------------------------------------------------------------------------
[Display(Name = " "), DataType(DataType.ImageUrl)]
public string Artwork2 { get; set; }
//----------------------------------------------------------------------------------------------
[Display(Name = " "), DataType(DataType.ImageUrl)]
public string Artwork3 { get; set; }
//----------------------------------------------------------------------------------------------
public virtual ICollection<Artwork> Artworks { get; set; }
}
public class ArtistDBContext : DbContext
{
public DbSet<Artist> Artists { get; set; }
public DbSet<Artwork> Artworks { get; set; }
}
public class Artwork
{
public int ArtworkID { get; set; }
//------------------------------------------------------------------------
//foreign key for Artists
public int ArtistID { get; set; }
//------------------------------------------------------------------------
[StringLength(60), Display(Name = "Artist")]
public string Name { get; set; }
//------------------------------------------------------------------------
[Required, DataType(DataType.ImageUrl)]
public string Picture { get; set; }
//------------------------------------------------------------------------
[DataType(DataType.MultilineText)]
public string Info { get; set; }
//------------------------------------------------------------------------
public virtual Artist Artist { get; set;}
}
迁移艺术品(1)
public override void Up()
{
DropPrimaryKey("dbo.Artists");
DropColumn("dbo.Artists", "ID");
CreateTable(
"dbo.Artworks",
c => new
{
ArtworkID = c.Int(nullable: false, identity: true),
ArtistID = c.Int(nullable: false),
Name = c.String(),
Info = c.String(),
})
.PrimaryKey(t => t.ArtworkID)
.ForeignKey("dbo.Artists", t => t.ArtistID, cascadeDelete: true)
.Index(t => t.ArtistID);
AddColumn("dbo.Artists", "ArtistID", c => c.Int(nullable: false, identity: true));
AddPrimaryKey("dbo.Artists", "ArtistID");
}
public override void Down()
{
DropForeignKey("dbo.Artworks", "ArtistID", "dbo.Artists");
DropIndex("dbo.Artworks", new[] { "ArtistID" });
DropPrimaryKey("dbo.Artists");
DropColumn("dbo.Artists", "ArtistID");
DropTable("dbo.Artworks");
AddColumn("dbo.Artists", "ID", c => c.Int(nullable: false, identity: true));
AddPrimaryKey("dbo.Artists", "ID");
}
迁移ArtworkAnnotations (2)
public override void Up()
{
AlterColumn("dbo.Artworks", "Name", c => c.String(nullable: false, maxLength: 60));
}
public override void Down()
{
AlterColumn("dbo.Artworks", "Name", c => c.String());
}
迁移图(3)
public override void Up()
{
AddColumn("dbo.Artworks", "Picture", c => c.String());
}
public override void Down()
{
DropColumn("dbo.Artworks", "Picture");
}
Config.cs
nternal sealed class Configuration : DbMigrationsConfiguration<ArtistDatabase.Models.ArtistDBContext>
{
public Configuration()
{
AutomaticMigrationsEnabled = false;
}
protected override void Seed(ArtistDatabase.Models.ArtistDBContext context)
{
context.Artists.AddOrUpdate(i => i.Name,
new Artist
{
ArtistID = 1,
Name = "Pablo Ruiz y Picasso",
Picture = "http://a5.files.biography.com/image/upload/c_fit,cs_srgb,dpr_1.0,h_1200,q_80,w_1200/MTE1ODA0OTcxNzU0MDk2MTQx.jpg",
BirthDate = DateTime.Parse("25-10-1881"),
Nationality = "Spanish",
ArtStyle = "Cubism, Surrealism",
Info = "Picasso was a Spanish painter, sculptor and ceramicist, among other things. He spent most of his adult life in France, " +
" and is regarding as one of the greatest and most influential artists of the 20th century. He is known as co-founding of the" +
" 'Cubist' movement; the invention of constructed sculpture, also being the co-inventor of collage, and for the wide variety" +
" of styles that he helped develop and explore. Picasso, Henri Matisse and Marcel Duchamp are regarded as the three artists" +
" who most defined the revolutionary developments in the plastic arts in the opening decades of the 20th century, responsible" +
" for significant developments in painting, sculpture, printmaking and ceramics. Picasso demonstrated extraordinary artistic" +
" talent in his early years, painting in a naturalistic manner through his childhood and adolescence.During the first decade" +
" of the 20th century, his style changed as he experimented with different theories, techniques, and ideas.His work is often" +
" categorized into periods.While the names of many of his later periods are debated, the most commonly accepted periods in his" +
" work are the Blue Period(1901–1904), the Rose Period(1904–1906), the African - influenced Period(1907–1909)," +
" Analytic Cubism(1909–1912),and Synthetic Cubism(1912–1919),also referred to as the Crystal period. Exceptionally prolific" +
" throughout the course of his long life, Picasso achieved universal renown and immense fortune for his revolutionary artistic" +
" accomplishments, and became one of the best - known figures in 20th - century art.",
Artwork1 = "https://s-media-cache-ak0.pinimg.com/originals/34/c4/8c/34c48c9178f215e2670feec774036803.jpg",
Artwork2 = "http://paintingandframe.com/uploadpic/pablo_picasso/big/les_demoiselles_d_avignon_c_1907.jpg",
Artwork3 = "http://www.pablopicasso.org/images/paintings/blue-nude.jpg"
},
new Artist
{
ArtistID = 2,
Name = "Leonardo da Vinci",
Picture = "http://www.leonardodavinci.net/images/leonardo-da-vinci.jpg",
BirthDate = DateTime.Parse("15-04-1452"),
Nationality = "Italian",
ArtStyle = "High Renaissance",
Info = "Leonardo di ser Piero da Vinci was an Italian polymath whose areas of interest included invention, painting," +
" sculpting, architecture, science, music, mathematics, engineering, literature, anatomy, geology, astronomy, botany, writing, history," +
" and cartography. He has been variously called the father of palaeontology, ichnology, and architecture, and is widely considered one" +
" of the greatest painters of all time. Sometimes credited with the inventions of the parachute, helicopter and tank, he epitomised" +
" the Renaissance humanist ideal.Many historians and scholars regard Leonardo as the prime exemplar of the 'Universal Genius' or " +
"'Renaissance Man', an individual of 'unquenchable curiosity' and 'feverishly inventive imagination'. According to art historian Helen" +
" Gardner, the scope and depth of his interests were without precedent in recorded history, and 'his mind and personality seem to us" +
" superhuman, while the man himself mysterious and remote'. Marco Rosci notes that while there is much speculation regarding his life" +
" and personality, his view of the world was logical rather than mysterious, and that the empirical methods he employed were unorthodox" +
" for his time. Leonardo was, and is, renowned primarily as a painter. Among his works, the Mona Lisa is the most famous and most" +
" parodied portrait and The Last Supper the most reproduced religious painting of all time, their fame approached only by Michelangelo's" +
" The Creation of Adam. Leonardo's drawing of the Vitruvian Man is also regarded as a cultural icon, being reproduced on items as" +
" varied as the euro coin, textbooks, and T-shirts. Perhaps fifteen of his paintings have survived. Nevertheless, these few works," +
" together with his notebooks, which contain drawings, scientific diagrams, and his thoughts on the nature of painting, compose a" +
" contribution to later generations of artists rivalled only by that of his contemporary, Michelangelo.",
Artwork1 = "https://upload.wikimedia.org/wikipedia/commons/thumb/e/ec/Mona_Lisa,_by_Leonardo_da_Vinci,_from_C2RMF_retouched.jpg/402px-Mona_Lisa,_by_Leonardo_da_Vinci,_from_C2RMF_retouched.jpg",
Artwork2 = "https://upload.wikimedia.org/wikipedia/commons/2/23/Leonardo_da_Vinci_-_Last_Supper_(copy)_-_WGA12732.jpg",
Artwork3 = "http://blog.world-mysteries.com/wp-content/uploads/2011/01/vitruvian_man_mixed.jpg"
},
new Artist
{
ArtistID = 3,
Name = "Georgia O'Keeffe",
Picture = "http://1874.img.pp.sohu.com.cn/images/blog/2008/11/16/20/26/11e4d90ce26g213.jpg",
BirthDate = DateTime.Parse("15-11-1887"),
Nationality = "American",
ArtStyle = "American Modernism",
Info = "Georgia Totto O'Keeffe was an American artist. She is best known for her paintings of enlarged flowers, New York skyscrapers," +
" and New Mexico landscapes. O'Keeffe has been recognized as the 'Mother of American modernism'. O'Keeffe studied at the School of the" +
" Art Institute of Chicago from 1905 to 1906. In 1907, she attended the Art Students League in New York City, where she studied under" +
" William Merritt Chase. In 1908, she won the League's William Merritt Chase still-life prize for her oil painting Dead Rabbit with" +
" Copper Pot. Her prize was a scholarship to attend the League's outdoor summer school in Lake George, New York. While in the city" +
" in 1908, O'Keeffe attended an exhibition of Rodin's watercolors at the gallery 291, owned by her future husband, photographer Alfred" +
" Stieglitz. O'Keeffe abandoned the idea of pursuing a career as an artist in late 1908, claiming that she could never distinguish" +
" herself as an artist within the mimetic tradition which had formed the basis of her art training. She took a job in Chicago as" +
" a commercial artist. She did not paint for four years, and said that the smell of turpentine made her sick. She was inspired to" +
" paint again in 1912, when she attended a class at the University of Virginia Summer School, where she was introduced to the innovative" +
" ideas of Arthur Wesley Dow by Alon Bement. Dow encouraged artists to express themselves using line, color, and shading" +
" harmoniously. From 1912-14, she taught art in the public schools in Amarillo in the Texas Panhandle. She attended Teachers College" +
" of Columbia University from 1914–15, where she took classes from Dow, who greatly influenced O'Keeffe's thinking about the process of" +
" making art. She served as a teaching assistant to Bement during the summers from 1913–16 and taught at Columbia College, Columbia," +
" South Carolina in late 1915, where she completed a series of highly innovative charcoal abstractions. After further course work at" +
" Columbia in early 1916 and summer teaching for Bement, she took a job as head of the art department at West Texas State Normal College" +
" from late 1916 to February 1918, the fledgling West Texas A&M University in Canyon just south of Amarillo. While there, she often" +
" visited the Palo Duro Canyon, making its forms a subject in her work.",
Artwork1 = "http://www.georgiaokeeffe.net/images/paintings/rams-head.jpg",
Artwork2 = "https://learnodo-newtonic.com/wp-content/uploads/2015/09/Red-Canna-1924-Georgia-OKeeffe.jpg",
Artwork3 = "http://www.themasterpiececards.com/hs-fs/hub/40667/file-25876050-jpg/images/okeeffe_jack_2_from_nga-resized-600.jpg?t=1465250810631"
},
new Artist
{
ArtistID = 4,
Name = "Vincent van Gogh",
Picture = "http://site.artsheaven.com/blog/wp-content/uploads/2015/10/vincent.jpg",
BirthDate = DateTime.Parse("30-03-1853"),
Nationality = "Dutch",
ArtStyle = "Post-Impressionism",
Info = "Vincent Willem van Gogh was a Dutch painter who is among the most famous and influential figures in the history of Western art." +
" In just over a decade he created about 2100 artworks, including around 860 oil paintings, most of them in the last two years of his" +
" life. They include landscapes, still lifes, portraits and self-portraits, and are characterised by bold, symbolic colours, and" +
" dramatic, impulsive and highly expressive brushwork that contributed to the foundations of modern art. He sold only one painting" +
" during his lifetime and became famous after his suicide at age 37, which followed years of poverty and mental illness. Van Gogh's" +
" early works, mostly still lifes and depictions of peasant labourers, contain few signs of the vivid colour that distinguished his" +
" later work. In 1886 he moved to Paris and discovered the French Impressionists. As his work developed he created a new approach to" +
" still lifes and local landscapes. His paintings grew brighter in colour as he developed a style that became fully realised during his" +
" stay in Arles in the south of France in 1888. He lived there in the Yellow House and, with the French artist Paul Gauguin, developed a" +
" concept of colour that symbolised inner emotion. During this period he broadened his subject matter to include olive trees, cypresses," +
" wheat fields and sunflowers. In Nuenen, Van Gogh focused on painting and drawing. Working outside and very quickly, he completed" +
" sketches and paintings of weavers and their cottages. In August 1884, Margot Begemann, a neighbour's daughter and ten years" +
" his senior, began joining him on his painting forays; she fell in love, and he reciprocated, though less enthusiastically. They" +
" decided to marry, but the idea was opposed by both families, following which Margot took an overdose of strychnine. She was saved" +
" when Van Gogh rushed her to a nearby hospital. On 26 March 1885, his father died of a heart attack. Van Gogh painted several" +
" groups of still lifes in 1885. During his two - year stay in Nuenen, he completed numerous drawings and watercolours, and nearly" +
" 200 oil paintings.His palette consisted mainly of sombre earth tones, particularly dark brown, and showed no sign of the vivid colours" +
" that distinguish his later work.Considered a madman and a failure in his lifetime,Van Gogh exists in the public imagination as the" +
" quintessential misunderstood genius, the artist 'where discourses on madness and creativity converge'.His reputation began to grow" +
" in the early 20th century as elements of his painting style came to be incorporated by the Fauves and German Expressionists.He attained" +
" widespread critical, commercial and popular success over the ensuing decades, and is remembered as an important but tragic painter," +
" whose troubled personality typifies the romantic ideal of the tortured artist.",
Artwork1 = "https://upload.wikimedia.org/wikipedia/commons/9/94/Starry_Night_Over_the_Rhone.jpg",
Artwork2 = "https://upload.wikimedia.org/wikipedia/commons/thumb/7/76/Vincent_van_Gogh_-_De_slaapkamer_-_Google_Art_Project.jpg/1280px-Vincent_van_Gogh_-_De_slaapkamer_-_Google_Art_Project.jpg",
Artwork3 = "https://upload.wikimedia.org/wikipedia/commons/thumb/b/b4/Vincent_Willem_van_Gogh_128.jpg/175px-Vincent_Willem_van_Gogh_128.jpg"
},
new Artist {
ArtistID = 5,
Name = "Salvador Dali",
Picture = "https://s-media-cache-ak0.pinimg.com/originals/4b/78/e7/4b78e72934aa5cdcb6a8bff7b23b4b51.jpg",
BirthDate = DateTime.Parse("11-05-1904"),
Nationality = "Spanish",
ArtStyle = "Cubism, Dada, Surrealism",
Info = "",
Artwork1 = "https://upload.wikimedia.org/wikipedia/en/4/43/Dali_Elephants.jpg",
Artwork2 = "http://www.dalipaintings.net/images/paintings/dream-caused-by-the-flight-of-a-bee.jpg",
Artwork3 = "http://www.dalipaintings.net/images/paintings/swans-reflecting-elephants.jpg",
},
new Artist
{
ArtistID = 6,
Name = "Andy Warhol",
Picture = "https://upload.wikimedia.org/wikipedia/commons/2/2b/Andy_Warhol_by_Jack_Mitchell.jpg",
BirthDate = DateTime.Parse("06-08-1928"),
Nationality = "American",
ArtStyle = "Pop art",
Info = "",
Artwork1 = "https://upload.wikimedia.org/wikipedia/en/thumb/1/1f/Campbells_Soup_Cans_MOMA.jpg/300px-Campbells_Soup_Cans_MOMA.jpg",
Artwork2 = "https://vmfa.museum/collections/wp-content/uploads/sites/9/2013/12/Warhol_85_453_v1_KW_200909_XL-878x1024.jpg",
Artwork3 = "https://cdn.kastatic.org/ka-perseus-images/329f84364bd08b80515b71fa830da2d2b6802c0c.jpg",
},
new Artist
{
ArtistID = 7,
Name = "Michelangelo",
Picture = "https://upload.wikimedia.org/wikipedia/commons/5/5e/Miguel_%C3%81ngel,_por_Daniele_da_Volterra_(detalle).jpg",
BirthDate = DateTime.Parse("06-03-1475"),
Nationality = "Italian",
ArtStyle = "High Renaissance",
Info = "",
Artwork1 = "https://upload.wikimedia.org/wikipedia/commons/b/b4/Michelangelo_-_Creation_of_Adam.jpg",
Artwork2 = "https://upload.wikimedia.org/wikipedia/commons/2/24/'David'_by_Michelangelo_JBU0001.JPG",
Artwork3 = "http://www.italianrenaissance.org/wp-content/uploads/2012/07/Michelangelo-pieta.jpg",
},
new Artist
{
ArtistID = 8,
Name = "Claude Monet",
Picture = "http://www.notesontheroad.com/images/stories/yings_links/Birthdays/Monet/claude-monet.jpg",
BirthDate = DateTime.Parse("14-11-1840"),
Nationality = "French",
ArtStyle = "Impressionism",
Info = "",
Artwork1 = "",
Artwork2 = "",
Artwork3 = "",
}
);
context.Artworks.AddOrUpdate(i => i.ArtistID,
new Artwork
{
ArtworkID = 1,
ArtistID = 1,
Name = "Guernica",
Picture = "https://upload.wikimedia.org/wikipedia/en/7/74/PicassoGuernica.jpg",
Info = "",
},
new Artwork
{
ArtworkID = 2,
ArtistID = 1,
Name = "The Weeping Woman",
Picture = "http://totallyhistory.com/wp-content/uploads/2012/12/pablo-picasso-weeping-woman.jpg",
Info = "",
},
new Artwork
{
ArtworkID = 3,
ArtistID = 1,
Name = "Three Musicians",
Picture = "http://www.pablopicasso.org/images/paintings/three-musicians.jpg",
Info = "",
},
new Artwork
{
ArtworkID = 4,
ArtistID = 1,
Name = "Le Rêve",
Picture = "https://upload.wikimedia.org/wikipedia/en/9/9d/Le-reve-1932.jpg",
Info = "",
}
);
当您播种Artworks时，您没有正确使用AddOrUpdate。
它需要一个唯一的标识符，所以不是:
context.Artworks.AddOrUpdate(i => i.ArtistID,
你应该使用:
context.Artworks.AddOrUpdate(i => i.ArtworkID,
您正在使用Linq方法SingleOrDefault，如果在查询中发现多个元素，将抛出异常。如果您预计谓词可以匹配多个元素，您可以使用方法FirstOrDefault，它将获得第一个匹配元素或返回null，如果没有找到或更改谓词更详细。