实体框架代码中的唯一约束

据我所知，目前无法使用 Entity Framework 执行此操作。但是，这不仅仅是唯一约束的问题……您可能还想创建索引、检查约束，还可能需要触发器和其他构造。 Here's a simple pattern you can use 使用您的代码优先设置，尽管不可否认它与数据库无关：

public class MyRepository : DbContext {
    public DbSet<Whatever> Whatevers { get; set; }

    public class Initializer : IDatabaseInitializer<MyRepository> {
        public void InitializeDatabase(MyRepository context) {
            if (!context.Database.Exists() || !context.Database.ModelMatchesDatabase()) {
                context.Database.DeleteIfExists();
                context.Database.Create();

                context.ObjectContext.ExecuteStoreCommand("CREATE UNIQUE CONSTRAINT...");
                context.ObjectContext.ExecuteStoreCommand("CREATE INDEX...");
                context.ObjectContext.ExecuteStoreCommand("ETC...");
            }
        }
    }
}

另一种选择是，如果您的域模型是在数据库中插入/更新数据的唯一方法，您可以自己实现唯一性要求并将数据库排除在外。这是一个更可移植的解决方案，并迫使您清楚代码中的业务规则，但会使您的数据库对无效数据开放，从而被后门入侵。

---

从 EF 6.1 开始，现在可以：

[Index(IsUnique = true)]
public string EmailAddress { get; set; }

严格来说，这将为您提供唯一索引而不是唯一约束。对于大多数实际用途they are the same。

---

与此无关，但在某些情况下可能会有所帮助。

如果您希望在假设 2 列上创建一个唯一的复合索引作为表的约束，那么从 4.3 版开始，您可以使用新的迁移机制来实现它：

http://msdn.microsoft.com/en-us/library/hh770484(v=vs.103).aspx

http://blogs.msdn.com/b/adonet/archive/2012/02/09/ef-4-3-code-based-migrations-walkthrough.aspx

基本上，您需要在其中一个迁移脚本中插入这样的调用：

CreateIndex("TableName", new string[2] { "Column1", "Column2" }, true, "IX_UniqueColumn1AndColumn2");

像这样的东西：

namespace Sample.Migrations
{
    using System;
    using System.Data.Entity.Migrations;

    public partial class TableName_SetUniqueCompositeIndex : DbMigration
    {
        public override void Up()
        {
            CreateIndex("TableName", new[] { "Column1", "Column2" }, true, "IX_UniqueColumn1AndColumn2");
        }

        public override void Down()
        {
            DropIndex("TableName", new[] { "Column1", "Column2" });
        }
    }
}

---

在创建数据库时，我做了一个完整的 hack 来执行 SQL。我创建自己的 DatabaseInitializer 并从提供的初始化程序之一继承。

public class MyDatabaseInitializer : RecreateDatabaseIfModelChanges<MyDbContext>
{
    protected override void Seed(MyDbContext context)
    {
        base.Seed(context);
        context.Database.Connection.StateChange += new StateChangeEventHandler(Connection_StateChange);
    }

    void Connection_StateChange(object sender, StateChangeEventArgs e)
    {
        DbConnection cnn = sender as DbConnection;

        if (e.CurrentState == ConnectionState.Open)
        {
            // execute SQL to create indexes and such
        }

        cnn.StateChange -= Connection_StateChange;
    }
}

这是我能找到插入我的 SQL 语句的唯一地方。

这是来自 CTP4。我不知道它在 CTP5 中是如何工作的。

---

只是想找出是否有办法做到这一点，到目前为止我发现的唯一方法是自己执行它，我创建了一个属性，以添加到每个类中，您需要在其中提供唯一的字段名称：

    [System.AttributeUsage(System.AttributeTargets.Class, AllowMultiple=false,Inherited=true)]
public class UniqueAttribute:System.Attribute
{
    private string[] _atts;
    public string[] KeyFields
    {
        get
        {
            return _atts;
        }
    }
    public UniqueAttribute(string keyFields)
    {
        this._atts = keyFields.Split(new char[]{','}, StringSplitOptions.RemoveEmptyEntries);
    }
}

然后在我的课上我会添加它：

[CustomAttributes.Unique("Name")]
public class Item: BasePOCO
{
    public string Name{get;set;}
    [StringLength(250)]
    public string Description { get; set; }
    [Required]
    public String Category { get; set; }
    [Required]
    public string UOM { get; set; }
    [Required]
}

最后，我将在我的存储库中、在 Add 方法中或在保存更改时添加一个方法，如下所示：

private void ValidateDuplicatedKeys(T entity)
{
    var atts = typeof(T).GetCustomAttributes(typeof(UniqueAttribute), true);
    if (atts == null || atts.Count() < 1)
    {
        return;
    }
    foreach (var att in atts)
    {
        UniqueAttribute uniqueAtt = (UniqueAttribute)att;
        var newkeyValues = from pi in entity.GetType().GetProperties()
                            join k in uniqueAtt.KeyFields on pi.Name equals k
                            select new { KeyField = k, Value = pi.GetValue(entity, null).ToString() };
        foreach (var item in _objectSet)
        {
            var keyValues = from pi in item.GetType().GetProperties()
                            join k in uniqueAtt.KeyFields on pi.Name equals k
                            select new { KeyField = k, Value = pi.GetValue(item, null).ToString() };
            var exists = keyValues.SequenceEqual(newkeyValues);
            if (exists)
            {
                throw new System.Exception("Duplicated Entry found");
            }
        }
    }
}

不太好，因为我们需要依赖反射，但到目前为止这是对我有用的方法！ =D

---

同样在 6.1 中，您可以像这样使用@mihkelmuur 答案的流畅语法版本：

Property(s => s.EmailAddress).HasColumnAnnotation(IndexAnnotation.AnnotationName,
new IndexAnnotation(
    new IndexAttribute("IX_UniqueEmail") { IsUnique = true }));

流利的方法不是完美的IMO，但至少现在是可能的。

更多关于 Arthur Vickers 博客的内容 http://blog.oneunicorn.com/2014/02/15/ef-6-1-creating-indexes-with-indexattribute/

---

在 Visual Basic 中使用 EF5 Code First 迁移的简单方法

公共课示例

    Public Property SampleId As Integer

    <Required>
    <MinLength(1),MaxLength(200)>

    Public Property Code() As String

结束类

MaxLength 属性对于字符串类型的唯一索引非常重要

运行 cmd：更新数据库 -verbose

运行 cmd: add-migration 1 后

在生成的文件中

Public Partial Class _1
    Inherits DbMigration

    Public Overrides Sub Up()
        CreateIndex("dbo.Sample", "Code", unique:=True, name:="IX_Sample_Code")
    End Sub

    Public Overrides Sub Down()
        'DropIndex if you need it
    End Sub

End Class

---

类似于 Tobias Schittkowski 的答案，但 C# 并且能够在约束中有多个字段。

要使用它，只需在您希望唯一的任何字段上放置一个 [Unique]。对于字符串，您必须执行以下操作（注意 MaxLength 属性）：

[Unique]
[MaxLength(450)] // nvarchar(450) is max allowed to be in a key
public string Name { get; set; }

因为默认字符串字段是 nvarchar(max) 并且不允许在键中使用。

对于约束中的多个字段，您可以执行以下操作：

[Unique(Name="UniqueValuePairConstraint", Position=1)]
public int Value1 { get; set; }
[Unique(Name="UniqueValuePairConstraint", Position=2)]
public int Value2 { get; set; }

一、UniqueAttribute：

/// <summary>
/// The unique attribute. Use to mark a field as unique. The
/// <see cref="DatabaseInitializer"/> looks for this attribute to 
/// create unique constraints in tables.
/// </summary>
internal class UniqueAttribute : Attribute
{
    /// <summary>
    /// Gets or sets the name of the unique constraint. A name will be 
    /// created for unnamed unique constraints. You must name your
    /// constraint if you want multiple fields in the constraint. If your 
    /// constraint has only one field, then this property can be ignored.
    /// </summary>
    public string Name { get; set; }

    /// <summary>
    /// Gets or sets the position of the field in the constraint, lower 
    /// numbers come first. The order is undefined for two fields with 
    /// the same position. The default position is 0.
    /// </summary>
    public int Position { get; set; }
}

然后，包括一个有用的扩展来从一个类型中获取数据库表名：

public static class Extensions
{
    /// <summary>
    /// Get a table name for a class using a DbContext.
    /// </summary>
    /// <param name="context">
    /// The context.
    /// </param>
    /// <param name="type">
    /// The class to look up the table name for.
    /// </param>
    /// <returns>
    /// The table name; null on failure;
    /// </returns>
    /// <remarks>
    /// <para>
    /// Like:
    /// <code>
    ///   DbContext context = ...;
    ///   string table = context.GetTableName&lt;Foo&gt;();
    /// </code>
    /// </para>
    /// <para>
    /// This code uses ObjectQuery.ToTraceString to generate an SQL 
    /// select statement for an entity, and then extract the table
    /// name from that statement.
    /// </para>
    /// </remarks>
    public static string GetTableName(this DbContext context, Type type)
    {
        return ((IObjectContextAdapter)context)
               .ObjectContext.GetTableName(type);
    }

    /// <summary>
    /// Get a table name for a class using an ObjectContext.
    /// </summary>
    /// <param name="context">
    /// The context.
    /// </param>
    /// <param name="type">
    /// The class to look up the table name for.
    /// </param>
    /// <returns>
    /// The table name; null on failure;
    /// </returns>
    /// <remarks>
    /// <para>
    /// Like:
    /// <code>
    ///   ObjectContext context = ...;
    ///   string table = context.GetTableName&lt;Foo&gt;();
    /// </code>
    /// </para>
    /// <para>
    /// This code uses ObjectQuery.ToTraceString to generate an SQL 
    /// select statement for an entity, and then extract the table
    /// name from that statement.
    /// </para>
    /// </remarks>
    public static string GetTableName(this ObjectContext context, Type type)
    {
        var genericTypes = new[] { type };
        var takesNoParameters = new Type[0];
        var noParams = new object[0];
        object objectSet = context.GetType()
                            .GetMethod("CreateObjectSet", takesNoParameters)
                            .MakeGenericMethod(genericTypes)
                            .Invoke(context, noParams);
        var sql = (string)objectSet.GetType()
                  .GetMethod("ToTraceString", takesNoParameters)
                  .Invoke(objectSet, noParams);
        Match match = 
            Regex.Match(sql, @"FROM\s+(.*)\s+AS", RegexOptions.IgnoreCase);
        return match.Success ? match.Groups[1].Value : null;
    }
}

然后，数据库初始化程序：

/// <summary>
///     The database initializer.
/// </summary>
public class DatabaseInitializer : IDatabaseInitializer<PedContext>
{
    /// <summary>
    /// Initialize the database.
    /// </summary>
    /// <param name="context">
    /// The context.
    /// </param>
    public void InitializeDatabase(FooContext context)
    {
        // if the database has changed, recreate it.
        if (context.Database.Exists()
            && !context.Database.CompatibleWithModel(false))
        {
            context.Database.Delete();
        }

        if (!context.Database.Exists())
        {
            context.Database.Create();

            // Look for database tables in the context. Tables are of
            // type DbSet<>.
            foreach (PropertyInfo contextPropertyInfo in 
                     context.GetType().GetProperties())
            {
                var contextPropertyType = contextPropertyInfo.PropertyType;
                if (contextPropertyType.IsGenericType
                    && contextPropertyType.Name.Equals("DbSet`1"))
                {
                    Type tableType = 
                        contextPropertyType.GetGenericArguments()[0];
                    var tableName = context.GetTableName(tableType);
                    foreach (var uc in UniqueConstraints(tableType, tableName))
                    {
                        context.Database.ExecuteSqlCommand(uc);
                    }
                }
            }

            // this is a good place to seed the database
            context.SaveChanges();
        }
    }

    /// <summary>
    /// Get a list of TSQL commands to create unique constraints on the given 
    /// table. Looks through the table for fields with the UniqueAttribute
    /// and uses those and the table name to build the TSQL strings.
    /// </summary>
    /// <param name="tableClass">
    /// The class that expresses the database table.
    /// </param>
    /// <param name="tableName">
    /// The table name in the database.
    /// </param>
    /// <returns>
    /// The list of TSQL statements for altering the table to include unique 
    /// constraints.
    /// </returns>
    private static IEnumerable<string> UniqueConstraints(
        Type tableClass, string tableName)
    {
        // the key is the name of the constraint and the value is a list 
        // of (position,field) pairs kept in order of position - the entry
        // with the lowest position is first.
        var uniqueConstraints = 
            new Dictionary<string, List<Tuple<int, string>>>();
        foreach (PropertyInfo entityPropertyInfo in tableClass.GetProperties())
        {
            var unique = entityPropertyInfo.GetCustomAttributes(true)
                         .OfType<UniqueAttribute>().FirstOrDefault();
            if (unique != null)
            {
                string fieldName = entityPropertyInfo.Name;

                // use the name field in the UniqueAttribute or create a
                // name if none is given
                string constraintName = unique.Name
                                        ?? string.Format(
                                            "constraint_{0}_unique_{1}",
                                            tableName
                                               .Replace("[", string.Empty)
                                               .Replace("]", string.Empty)
                                               .Replace(".", "_"),
                                            fieldName);

                List<Tuple<int, string>> constraintEntry;
                if (!uniqueConstraints.TryGetValue(
                        constraintName, out constraintEntry))
                {
                    uniqueConstraints.Add(
                        constraintName, 
                        new List<Tuple<int, string>> 
                        {
                            new Tuple<int, string>(
                                unique.Position, fieldName) 
                        });
                }
                else
                {
                    // keep the list of fields in order of position
                    for (int i = 0; ; ++i)
                    {
                        if (i == constraintEntry.Count)
                        {
                            constraintEntry.Add(
                                new Tuple<int, string>(
                                    unique.Position, fieldName));
                            break;
                        }

                        if (unique.Position < constraintEntry[i].Item1)
                        {
                            constraintEntry.Insert(
                                i, 
                                new Tuple<int, string>(
                                    unique.Position, fieldName));
                            break;
                        }
                    }
                }
            }
        }

        return
            uniqueConstraints.Select(
                uc =>
                string.Format(
                    "ALTER TABLE {0} ADD CONSTRAINT {1} UNIQUE ({2})",
                    tableName,
                    uc.Key,
                    string.Join(",", uc.Value.Select(v => v.Item2))));
    }
}

---

我通过反思解决了这个问题（对不起，伙计们，VB.Net ...）

首先，定义一个属性 UniqueAttribute：

<AttributeUsage(AttributeTargets.Property, AllowMultiple:=False, Inherited:=True)> _
Public Class UniqueAttribute
    Inherits Attribute

End Class

然后，增强您的模型，例如

<Table("Person")> _
Public Class Person

    <Unique()> _
    Public Property Username() As String

End Class

最后，创建一个自定义 DatabaseInitializer （在我的版本中，只有在调试模式下，我才会在 DB 更改上重新创建 DB ...）。在此 DatabaseInitializer 中，索引是根据唯一属性自动创建的：

Imports System.Data.Entity
Imports System.Reflection
Imports System.Linq
Imports System.ComponentModel.DataAnnotations

Public Class DatabaseInitializer
    Implements IDatabaseInitializer(Of DBContext)

    Public Sub InitializeDatabase(context As DBContext) Implements IDatabaseInitializer(Of DBContext).InitializeDatabase
        Dim t As Type
        Dim tableName As String
        Dim fieldName As String

        If Debugger.IsAttached AndAlso context.Database.Exists AndAlso Not context.Database.CompatibleWithModel(False) Then
            context.Database.Delete()
        End If

        If Not context.Database.Exists Then
            context.Database.Create()

            For Each pi As PropertyInfo In GetType(DBContext).GetProperties
                If pi.PropertyType.IsGenericType AndAlso _
                    pi.PropertyType.Name.Contains("DbSet") Then

                    t = pi.PropertyType.GetGenericArguments(0)

                    tableName = t.GetCustomAttributes(True).OfType(Of TableAttribute).FirstOrDefault.Name
                    For Each piEntity In t.GetProperties
                        If piEntity.GetCustomAttributes(True).OfType(Of Model.UniqueAttribute).Any Then

                            fieldName = piEntity.Name
                            context.Database.ExecuteSqlCommand("ALTER TABLE " & tableName & " ADD CONSTRAINT con_Unique_" & tableName & "_" & fieldName & " UNIQUE (" & fieldName & ")")

                        End If
                    Next
                End If
            Next

        End If

    End Sub

End Class

也许这有帮助...

---

Fluent Api 解决方案：

modelBuilder.Entity<User>(entity =>
{
    entity.HasIndex(e => e.UserId)
          .HasName("IX_User")
          .IsUnique();

    entity.HasAlternateKey(u => u.Email);

    entity.HasIndex(e => e.Email)
          .HasName("IX_Email")
          .IsUnique();
});

---

如果您在 DbContext 类中覆盖 ValidateEntity 方法，您也可以将逻辑放在那里。这样做的好处是您可以完全访问所有 DbSet。这是一个例子：

using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using System.Data.Entity.ModelConfiguration.Conventions;
using System.Data.Entity.Validation;
using System.Linq;

namespace MvcEfClient.Models
{
    public class Location
    {
        [Key]
        public int LocationId { get; set; }

        [Required]
        [StringLength(50)]
        public string Name { get; set; }
    }

    public class CommitteeMeetingContext : DbContext
    {
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
        }

        protected override DbEntityValidationResult ValidateEntity(DbEntityEntry entityEntry, IDictionary<object, object> items)
        {
            List<DbValidationError> validationErrors = new List<DbValidationError>();

            // Check for duplicate location names

            if (entityEntry.Entity is Location)
            {
                Location location = entityEntry.Entity as Location;

                // Select the existing location

                var existingLocation = (from l in Locations
                                        where l.Name == location.Name && l.LocationId != location.LocationId
                                        select l).FirstOrDefault();

                // If there is an existing location, throw an error

                if (existingLocation != null)
                {
                    validationErrors.Add(new DbValidationError("Name", "There is already a location with the name '" + location.Name + "'"));
                    return new DbEntityValidationResult(entityEntry, validationErrors);
                }
            }

            return base.ValidateEntity(entityEntry, items);
        }

        public DbSet<Location> Locations { get; set; }
    }
}

---

如果您使用的是 EF5 并且仍然有这个问题，下面的解决方案为我解决了这个问题。

我正在使用代码优先方法，因此放置：

this.Sql("CREATE UNIQUE NONCLUSTERED INDEX idx_unique_username ON dbo.Users(Username) WHERE Username IS NOT NULL;");

在迁移脚本中做得很好。它还允许 NULL 值！

---

使用 EF Code First 方法，可以使用以下技术实现基于属性的唯一约束支持。

创建标记属性

[AttributeUsage(AttributeTargets.Property)]
public class UniqueAttribute : System.Attribute { }

标记您希望在实体上具有唯一性的属性，例如

[Unique]
public string EmailAddress { get; set; }

创建数据库初始化程序或使用现有初始化程序来创建唯一约束

public class DbInitializer : IDatabaseInitializer<DbContext>
{
    public void InitializeDatabase(DbContext db)
    {
        if (db.Database.Exists() && !db.Database.CompatibleWithModel(false))
        {
            db.Database.Delete();
        }

        if (!db.Database.Exists())
        {
            db.Database.Create();
            CreateUniqueIndexes(db);
        }
    }

    private static void CreateUniqueIndexes(DbContext db)
    {
        var props = from p in typeof(AppDbContext).GetProperties()
                    where p.PropertyType.IsGenericType
                       && p.PropertyType.GetGenericTypeDefinition()
                       == typeof(DbSet<>)
                    select p;

        foreach (var prop in props)
        {
            var type = prop.PropertyType.GetGenericArguments()[0];
            var fields = from p in type.GetProperties()
                         where p.GetCustomAttributes(typeof(UniqueAttribute),
                                                     true).Any()
                         select p.Name;

            foreach (var field in fields)
            {
                const string sql = "ALTER TABLE dbo.[{0}] ADD CONSTRAINT"
                                 + " [UK_dbo.{0}_{1}] UNIQUE ([{1}])";
                var command = String.Format(sql, type.Name, field);
                db.Database.ExecuteSqlCommand(command);
            }
        }
    }   
}

设置您的数据库上下文以在启动代码中使用此初始化程序（例如在 main() 或 Application_Start() 中）

Database.SetInitializer(new DbInitializer());

解决方案类似于 mheyman 的，简化为不支持复合键。与 EF 5.0+ 一起使用。

---

我今天遇到了这个问题，最后我能够解决它。我不知道这是否是正确的方法，但至少我可以继续前进：

public class Person : IValidatableObject
{
    public virtual int ID { get; set; }
    public virtual string Name { get; set; }


    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
    {
        var field = new[] { "Name" }; // Must be the same as the property

        PFContext db = new PFContext();

        Person person = validationContext.ObjectInstance as Person;

        var existingPerson = db.Persons.FirstOrDefault(a => a.Name == person.Name);

        if (existingPerson != null)
        {
            yield return new ValidationResult("That name is already in the db", field);
        }
    }
}

---

使用唯一的属性验证器。

protected override DbEntityValidationResult ValidateEntity(DbEntityEntry entityEntry, IDictionary<object, object> items) {
   var validation_state = base.ValidateEntity(entityEntry, items);
   if (entityEntry.Entity is User) {
       var entity = (User)entityEntry.Entity;
       var set = Users;

       //check name unique
       if (!(set.Any(any_entity => any_entity.Name == entity.Name))) {} else {
           validation_state.ValidationErrors.Add(new DbValidationError("Name", "The Name field must be unique."));
       }
   }
   return validation_state;
}

ValidateEntity 不在同一个数据库事务中调用。因此，可能与数据库中的其他实体存在竞争条件。您必须稍微破解 EF 以强制围绕 SaveChanges（因此，ValidateEntity）进行事务。 DBContext 不能直接打开连接，但 ObjectContext 可以。

using (TransactionScope transaction = new TransactionScope(TransactionScopeOption.Required)) {
   ((IObjectContextAdapter)data_context).ObjectContext.Connection.Open();
   data_context.SaveChanges();
   transaction.Complete();
}

---

根据 http://blogs.msdn.com/b/adonet/archive/2014/02/11/ef-6-1-0-beta-1-available.aspx，EF 6.1 将有一个 IndexAttribute 来帮助我们。

---

阅读此问题后，我在尝试实现将属性指定为唯一键（如 Mihkel Müür's、Tobias Schittkowski's 和 mheyman's）的过程中遇到了自己的问题，答案建议：Map Entity Framework code properties to database columns (CSpace to SSpace)

我终于得到了这个答案，它可以将标量和导航属性映射到数据库列，并以属性上指定的特定顺序创建唯一索引。此代码假定您已实现具有 Sequence 属性的 UniqueAttribute，并将其应用于应表示实体的唯一键（主键除外）的 EF 实体类属性。

注意：此代码依赖于 EF 版本 6.1（或更高版本），它公开了以前版本中不可用的 EntityContainerMapping。

Public Sub InitializeDatabase(context As MyDB) Implements IDatabaseInitializer(Of MyDB).InitializeDatabase
    If context.Database.CreateIfNotExists Then
        Dim ws = DirectCast(context, System.Data.Entity.Infrastructure.IObjectContextAdapter).ObjectContext.MetadataWorkspace
        Dim oSpace = ws.GetItemCollection(Core.Metadata.Edm.DataSpace.OSpace)
        Dim entityTypes = oSpace.GetItems(Of EntityType)()
        Dim entityContainer = ws.GetItems(Of EntityContainer)(DataSpace.CSpace).Single()
        Dim entityMapping = ws.GetItems(Of EntityContainerMapping)(DataSpace.CSSpace).Single.EntitySetMappings
        Dim associations = ws.GetItems(Of EntityContainerMapping)(DataSpace.CSSpace).Single.AssociationSetMappings
        For Each setType In entityTypes
           Dim cSpaceEntitySet = entityContainer.EntitySets.SingleOrDefault( _
              Function(t) t.ElementType.Name = setType.Name)
           If cSpaceEntitySet Is Nothing Then Continue For ' Derived entities will be skipped
           Dim sSpaceEntitySet = entityMapping.Single(Function(t) t.EntitySet Is cSpaceEntitySet)
           Dim tableInfo As MappingFragment
           If sSpaceEntitySet.EntityTypeMappings.Count = 1 Then
              tableInfo = sSpaceEntitySet.EntityTypeMappings.Single.Fragments.Single
           Else
              ' Select only the mapping (esp. PropertyMappings) for the base class
              tableInfo = sSpaceEntitySet.EntityTypeMappings.Where(Function(m) m.IsOfEntityTypes.Count _
                 = 1 AndAlso m.IsOfEntityTypes.Single.Name Is setType.Name).Single().Fragments.Single
           End If
           Dim tableName = If(tableInfo.StoreEntitySet.Table, tableInfo.StoreEntitySet.Name)
           Dim schema = tableInfo.StoreEntitySet.Schema
           Dim clrType = Type.GetType(setType.FullName)
           Dim uniqueCols As IList(Of String) = Nothing
           For Each propMap In tableInfo.PropertyMappings.OfType(Of ScalarPropertyMapping)()
              Dim clrProp = clrType.GetProperty(propMap.Property.Name)
              If Attribute.GetCustomAttribute(clrProp, GetType(UniqueAttribute)) IsNot Nothing Then
                 If uniqueCols Is Nothing Then uniqueCols = New List(Of String)
                 uniqueCols.Add(propMap.Column.Name)
              End If
           Next
           For Each navProp In setType.NavigationProperties
              Dim clrProp = clrType.GetProperty(navProp.Name)
              If Attribute.GetCustomAttribute(clrProp, GetType(UniqueAttribute)) IsNot Nothing Then
                 Dim assocMap = associations.SingleOrDefault(Function(a) _
                    a.AssociationSet.ElementType.FullName = navProp.RelationshipType.FullName)
                 Dim sProp = assocMap.Conditions.Single
                 If uniqueCols Is Nothing Then uniqueCols = New List(Of String)
                 uniqueCols.Add(sProp.Column.Name)
              End If
           Next
           If uniqueCols IsNot Nothing Then
              Dim propList = uniqueCols.ToArray()
              context.Database.ExecuteSqlCommand("CREATE UNIQUE INDEX IX_" & tableName & "_" & String.Join("_", propList) _
                 & " ON " & schema & "." & tableName & "(" & String.Join(",", propList) & ")")
           End If
        Next
    End If
End Sub

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对于那些使用代码优先配置的用户，您还可以将 IndexAttribute 对象用作 ColumnAnnotation 并将其 IsUnique 属性设置为 true。

例如：

var indexAttribute = new IndexAttribute("IX_name", 1) {IsUnique = true};

Property(i => i.Name).HasColumnAnnotation("Index",new IndexAnnotation(indexAttribute));

这将在 Name 列上创建一个名为 IX_name 的唯一索引。

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很抱歉回答晚了，但我发现和你一起分享它很好

我已在 code project 上发布了相关信息

通常，它取决于您放在类上的属性来生成唯一索引

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