我在我的项目中有一个下面的模型
public class Category
{
public Guid ID { get; set; }
[Required(ErrorMessage = "Title cannot be empty")]
public string Title { get; set; }
}
我想将Title
作为唯一键,我在Google上搜索了解决方案,但没有找到任何内容。请问有人可以建议我如何做吗?
我在我的项目中有一个下面的模型
public class Category
{
public Guid ID { get; set; }
[Required(ErrorMessage = "Title cannot be empty")]
public string Title { get; set; }
}
我想将Title
作为唯一键,我在Google上搜索了解决方案,但没有找到任何内容。请问有人可以建议我如何做吗?
不幸的是,你无法在代码优先中将其定义为唯一键,因为EF根本不支持唯一键(希望在下一个主要版本中计划支持)。你可以做的是创建自定义数据库初始化器,并通过调用SQL命令手动添加唯一索引:
public class MyInitializer : CreateDatabaseIfNotExists<MyContext>
{
protected override void Seed(MyContext context)
{
context.Database.ExecuteSqlCommand("CREATE UNIQUE INDEX IX_Category_Title ON Categories (Title)");
}
}
你必须在应用程序的引导程序中设置此初始化器。
Database.SetInitializer<MyContext>(new MyInitializer());
编辑
现在(EF 6.1及以上版本),您可以轻松地设置唯一约束,
[Index("TitleIndex", IsUnique = true)]
public string Title { get; set; }
首先创建自定义属性类:
[AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
public class UniqueAttribute : ValidationAttribute
{
public override Boolean IsValid(Object value)
{
// constraint implemented on database
return true;
}
}
public class Email
{
[Key]
public int EmailID { get; set; }
public int PersonId { get; set; }
[Unique]
[Required]
[MaxLength(100)]
public string EmailAddress { get; set; }
public virtual bool IsDefault { get; set; }
public virtual Boolean IsApprovedForLogin { get; set; }
public virtual String ConfirmationToken { get; set; }
[ForeignKey("PersonId")]
public virtual Person Person { get; set; }
}
然后在您的DbContext上添加一个初始化器:
public class Initializer : IDatabaseInitializer<myEntities>
{
public void InitializeDatabase(myEntities context)
{
if (System.Diagnostics.Debugger.IsAttached && context.Database.Exists() && !context.Database.CompatibleWithModel(false))
{
context.Database.Delete();
}
if (!context.Database.Exists())
{
context.Database.Create();
var contextObject = context as System.Object;
var contextType = contextObject.GetType();
var properties = contextType.GetProperties();
System.Type t = null;
string tableName = null;
string fieldName = null;
foreach (var pi in properties)
{
if (pi.PropertyType.IsGenericType && pi.PropertyType.Name.Contains("DbSet"))
{
t = pi.PropertyType.GetGenericArguments()[0];
var mytableName = t.GetCustomAttributes(typeof(TableAttribute), true);
if (mytableName.Length > 0)
{
TableAttribute mytable = mytableName[0] as TableAttribute;
tableName = mytable.Name;
}
else
{
tableName = pi.Name;
}
foreach (var piEntity in t.GetProperties())
{
if (piEntity.GetCustomAttributes(typeof(UniqueAttribute), true).Length > 0)
{
fieldName = piEntity.Name;
context.Database.ExecuteSqlCommand("ALTER TABLE " + tableName + " ADD CONSTRAINT con_Unique_" + tableName + "_" + fieldName + " UNIQUE (" + fieldName + ")");
}
}
}
}
}
}
}
System.Data.Entity.Database.SetInitializer<MyApp.Models.DomainModels.myEntities>(new MyApp.Models.DomainModels.myEntities.Initializer());
就是这样。基于https://dev59.com/h2855IYBdhLWcg3wUSgW#7426773上的VB代码。
这里是VB.Net版本 - 请注意泛型的实现在类级别上有所不同。
Public Class MyInitializer(Of T As DbContext)
Inherits CreateDatabaseIfNotExists(Of T)
Protected Overrides Sub Seed(context As T)
context.Database.ExecuteSqlCommand("CREATE UNIQUE INDEX IX_Category_Title ON Categories (Title)")
End Sub
End Class
using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
//dll Microsoft.SqlServer.Smo
//dll Microsoft.SqlServer.Management.Sdk.Sfc
//dll Microsoft.SqlServer.ConnectionInfo
using Microsoft.SqlServer.Management.Common;
using Microsoft.SqlServer.Management.Smo;
using Monitor.Common;
namespace MonitorDB.DataLayer.Migrations
{
public class ExecuteSQLScripts :Monitor.Common.ExceptionHandling
{
public ExecuteSQLScripts()
{
}
public bool ExecuteScriptsInDirectory(DBContext.SolArcMsgMonitorContext context, string scriptDirectory)
{
bool Result = false;
try
{
SqlConnection connection = new SqlConnection(context.Database.Connection.ConnectionString);
Server server = new Server(new ServerConnection(connection));
DirectoryInfo di = new DirectoryInfo(scriptDirectory);
FileInfo[] rgFiles = di.GetFiles("*.sql");
foreach (FileInfo fi in rgFiles)
{
FileInfo fileInfo = new FileInfo(fi.FullName);
string script = fileInfo.OpenText().ReadToEnd();
server.ConnectionContext.ExecuteNonQuery(script);
}
Result = true;
}
catch (Exception ex)
{
CatchException("ExecuteScriptsInDirectory", ex);
}
return Result;
}
这里是 VS 解决方案的样子:
}
ExecuteStoreCommand
。 - Ladislav Mrnka