<分区>
有没有办法使用数据注释来定义唯一索引？
假设我有一个类:
public class User
{
[Key]
public int UserID { get; set; }
public string UserName { get; set; }
public string Email { get; set; }
}
如果我希望电子邮件是唯一的，我该如何为其添加唯一索引？
<分区>
有没有办法使用数据注释来定义唯一索引？
假设我有一个类:
public class User
{
[Key]
public int UserID { get; set; }
public string UserName { get; set; }
public string Email { get; set; }
}
如果我希望电子邮件是唯一的，我该如何为其添加唯一索引？
最佳答案
这与我已经回答过的问题很接近 MVC Model - create db index
根据此链接:Creating Indexes via Data Annotations with Entity Framework 5.0 你应该写一些扩展代码:
using System;
[AttributeUsage(AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
public class IndexAttribute : Attribute
{
public IndexAttribute(string name, bool unique = false)
{
this.Name = name;
this.IsUnique = unique;
}
public string Name { get; private set; }
public bool IsUnique { get; private set; }
}
第二类:
using System.ComponentModel.DataAnnotations.Schema;
using System.Data.Entity;
using System.Linq;
using System.Reflection;
public class IndexInitializer<T> : IDatabaseInitializer<T> where T : DbContext
{
private const string CreateIndexQueryTemplate = "CREATE {unique} INDEX {indexName} ON {tableName} ({columnName})";
public void InitializeDatabase(T context)
{
const BindingFlags PublicInstance = BindingFlags.Public | BindingFlags.Instance;
foreach (var dataSetProperty in typeof(T).GetProperties(PublicInstance).Where(
p => p.PropertyType.Name == typeof(DbSet<>).Name))
{
var entityType = dataSetProperty.PropertyType.GetGenericArguments().Single();
TableAttribute[] tableAttributes = (TableAttribute[])entityType.GetCustomAttributes(typeof(TableAttribute), false);
foreach (var property in entityType.GetProperties(PublicInstance))
{
IndexAttribute[] indexAttributes = (IndexAttribute[])property.GetCustomAttributes(typeof(IndexAttribute), false);
NotMappedAttribute[] notMappedAttributes = (NotMappedAttribute[])property.GetCustomAttributes(typeof(NotMappedAttribute), false);
if (indexAttributes.Length > 0 && notMappedAttributes.Length == 0)
{
ColumnAttribute[] columnAttributes = (ColumnAttribute[])property.GetCustomAttributes(typeof(ColumnAttribute), false);
foreach (var indexAttribute in indexAttributes)
{
string indexName = indexAttribute.Name;
string tableName = tableAttributes.Length != 0 ? tableAttributes[0].Name : dataSetProperty.Name;
string columnName = columnAttributes.Length != 0 ? columnAttributes[0].Name : property.Name;
string query = CreateIndexQueryTemplate.Replace("{indexName}", indexName)
.Replace("{tableName}", tableName)
.Replace("{columnName}", columnName)
.Replace("{unique}", indexAttribute.IsUnique ? "UNIQUE" : string.Empty);
context.Database.CreateIfNotExists();
context.Database.ExecuteSqlCommand(query);
}
}
}
}
}
}
之后你可以这样使用你的index:
[Required]
[Index("IMEIIndex", unique: true)]
[StringLength(15)]
public string IMEI { get; set; }
关于c# - 使用数据注释的唯一索引，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/19023958/