• EF 学习笔记

    1、一次性添加映射

     1     public class EntityDbContext : DbContext 
 2     {  
 3         public EntityDbContext()
 4             : base("name=test2")
 5         { }
 6 
 7 
 8         /// <summary>
 9         /// 通过反射一次性将表进行映射
10         /// </summary>
11         /// <param name="modelBuilder"></param>
12         protected override void OnModelCreating(DbModelBuilder modelBuilder)
13         {
14            
15             var typesRegister = Assembly.GetExecutingAssembly().GetTypes()
16                 .Where(type => !(string.IsNullOrEmpty(type.Namespace))).Where(type => type.BaseType != null && type.BaseType.IsGenericType && type.BaseType.GetGenericTypeDefinition() == typeof(EntityTypeConfiguration<>));
17             foreach (var type in typesRegister)
18             {
19                 dynamic configurationInstance = Activator.CreateInstance(type);
20                 modelBuilder.Configurations.Add(configurationInstance);
21             }
22 
23         }
24     }
    View Code
     1     public class StudentMap : EntityTypeConfiguration<Student>
 2     {
 3         public StudentMap()
 4         {
 5             ToTable("Student");
 6             HasKey(d => d.ID);
 7           
 8             //HasRequired(p => p.Course).WithRequiredDependent(i => i.Student);           
 9             //HasRequired(p => p.Course).WithOptional(i => i.Student);
10 
11             HasRequired(p => p.Course).WithRequiredPrincipal(p => p.Student);
12             HasOptional(p => p.Course).WithRequired(p => p.Student);
13 
14             /*
15              对于上述映射关系不太理解的话可以去上述给出链接文章。我只说明怎么去很好的理解这两组的意思，第一组 WithRequiredDependent 和第二组
16              WithRequiredPrincipal 一个是Dependent是依赖的意思说明后面紧接着的Student是依赖对象，而前面的Course是主体，而Principal
17              首先的意思，说明后面紧接着的是Student是主体，而Course是依赖对象。很显然在这个关系中课程是依赖学生的。所以映射选第二组  
18             */
19         }
20     }
    StudentMap

    2、延迟加载必须满足三个条件：

    1. this.Configuration.ProxyCreationEnabled = true;
    2. this.Configuration.LazyLoadingEnabled = true;
    3. 导航属性修饰符必须为Virtual

    3、映射private/protected/internal属性：

    1     public class Student
2     {
3         public string Id { get; set; }
4         public string Name { get; set; }
5         private string TestPrivate { get; set; }
6         internal string TestInternal { get; set; }
7         protected string TestProtected { get; set; }
8     ｝
     1 　　public class BreakAwayContext : DbContext
 2     {
 3         public BreakAwayContext()
 4             : base("name=BreakAwayContext")
 5         {
 6             this.Configuration.LazyLoadingEnabled = false;//对所有实体关闭惰性加载
 7             this.Configuration.ProxyCreationEnabled = false;//禁止创建代理
 8 
 9             DbInterception.Add(new NLogCommandInterceptor());
10         }
11 
12         protected override void OnModelCreating(DbModelBuilder modelBuilder)
13         {
14             ////<EF 6.0
15             //modelBuilder.Entities().Configure(c =>
16             //{
17             //    var nonPublicProperties = c.ClrType.GetProperties(BindingFlags.NonPublic | BindingFlags.Instance);
18 
19             //    foreach (var p in nonPublicProperties)
20             //    {
21             //        c.Property(p).HasColumnName(p.Name);
22             //    }
23             //});
24             //EF 6.0
25             modelBuilder.Types().Configure(d =>
26             {
27                 var nonPublicProperties = d.ClrType.GetProperties(BindingFlags.NonPublic | BindingFlags.Instance);
28                 foreach (var p in nonPublicProperties)
29                 {
30                     d.Property(p).HasColumnName(p.Name);
31                 }
32             });
33             modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
34         }
35 
36         public DbSet<Student> Students { get; set; }
37 
38     }

    4、各种查询：

    条件查询

    1 　　　　var sql = "select ID, Name, Age from Student where Name = @Name and Age = @Age";
2 
3  　　　 ctx.Database.SqlQuery<Student>(
4                 sql, 
5                 new SqlParameter("@Name", Name),
6                 new SqlParameter("@Age", Age));

    非实体查询

    ctx.Database.SqlQuery<int>("select Age from Student").ToList();

     执行存储过程

    ctx.Database.SqlQuery<Student>("dbo.GetList").ToList();
     var param = new SqlParameter("Age", 5);
 var list = ctx.Database.SqlQuery<Student>("dbo.GetList @Age", param).ToList();

/*查询出的所有列必须对应返回实体中的所有字段，缺一不可，否则报错！在调用存储过程中，如果数据库是Sql 2005要在存储过程名称前加上 EXEC,否则报错*/
    　　　　　　　var name = new SqlParameter { ParameterName = "Name", Value = Name };
            var currentpage = new SqlParameter { ParameterName = "PageIndex", Value = currentPage };
            var pagesize = new SqlParameter { ParameterName = "PageSize", Value = pageSize };
            var totalcount = new SqlParameter { ParameterName = "TotalCount", Value = 0, Direction = ParameterDirection.Output };

            var list = ctx.Database.SqlQuery<Student>("Myproc @Name, @PageIndex, @PageSize, @TotalCount output",
        name, currentpage, pagesize, totalcount);

            totalCount = (int)totalcount.Value;  /*获得要输出参数totalcount的值*/
     1 public IList<TEntity> ExecuteStoredProcedureList<TEntity>(string commandText, params object[] parameters) where TEntity : class
 2         {
 3             if (parameters != null && parameters.Length > 0)
 4             {
 5                 for (int i = 0; i <= parameters.Length - 1; i++)
 6                 {
 7                     var p = parameters[i] as DbParameter;
 8                     if (p == null)
 9                         throw new Exception("Not support parameter type");
10 
11                     commandText += i == 0 ? " " : ", ";
12 
13                     commandText += "@" + p.ParameterName;
14                     if (p.Direction == ParameterDirection.InputOutput || p.Direction == ParameterDirection.Output)
15                     {
16 
17                         commandText += " output";
18                     }
19                 }
20             }
21 
22             var result = this.Database.SqlQuery<TEntity>(commandText, parameters).ToList();
23 
24  
25             bool acd = this.Configuration.AutoDetectChangesEnabled;
26             
27             try
28             {
29                 this.Configuration.AutoDetectChangesEnabled = false;
30 
31                 for (int i = 0; i < result.Count; i++)
32                     result[i] = this.Set<TEntity>().Attach(result[i]);
33             }
34             finally
35             {
36                 this.Configuration.AutoDetectChangesEnabled = acd;
37             }
38 
39             return result;
40         }
    调用存储过程封装
    var list = ctx.ExecuteStoredProcedureList<Student>("Myproc", pageindex, pagesize, totalcount);

    5、EF在查询之前进行操作来忽略尾随空格

     1     public class EFConfiguration : DbConfiguration
 2     {
 3         public EFConfiguration()
 4         {
 5             AddInterceptor(new StringTrimmerInterceptor());
 6         }
 7     }
 8     public class StringTrimmerInterceptor : IDbCommandTreeInterceptor
 9     {
10         public void TreeCreated(DbCommandTreeInterceptionContext interceptionContext)
11         {
12             if (interceptionContext.OriginalResult.DataSpace == DataSpace.SSpace)
13             {
14                 var queryCommand = interceptionContext.Result as DbQueryCommandTree;
15                 if (queryCommand != null)
16                 {
17                     var newQuery = queryCommand.Query.Accept(new StringTrimmerQueryVisitor());
18                     interceptionContext.Result = new DbQueryCommandTree(
19                         queryCommand.MetadataWorkspace,
20                         queryCommand.DataSpace,
21                         newQuery);
22                 }
23             }
24         }
25 
26         private class StringTrimmerQueryVisitor : DefaultExpressionVisitor
27         {
28             private static readonly string[] _typesToTrim = { "nvarchar", "varchar", "char", "nchar" };
29 
30             public override DbExpression Visit(DbNewInstanceExpression expression)
31             {
32                 var arguments = expression.Arguments.Select(a =>
33                 {
34                     var propertyArg = a as DbPropertyExpression;
35                     if (propertyArg != null&& _typesToTrim.Contains(propertyArg.Property.TypeUsage.EdmType.Name))
36                     {
37                         return EdmFunctions.Trim(a);
38                     }
39  
40                     return a;
41                 });
42  
43                 return DbExpressionBuilder.New(expression.ResultType, arguments);
44             }
45         }
46     }
    EF在查询之前进行操作来忽略尾随空格

    6、扩展方法

     1     public static class EFExt
 2     {
 3         /// <summary>
 4         /// 获得实体的所有键的名称
 5         /// </summary>
 6         /// <param name="ctx"></param>
 7         /// <param name="entity"></param>
 8         /// <returns></returns>
 9         static string[] GetKeyNames(this DbContext ctx, Type entity)
10         {
11             var metadata = ((IObjectContextAdapter)ctx).ObjectContext.MetadataWorkspace;
12 
13             /*获得CLR type集合和medata OSpace之间的映射*/
14             var objItemCollection = (ObjectItemCollection)metadata.GetItemCollection(DataSpace.OSpace);
15 
16             /*根据所给的CLR type获得实体的元数据即metadata*/
17             var entitydata = metadata.GetItems<EntityType>(DataSpace.OSpace).Single(e => objItemCollection.GetClrType(e) == entity);
18             /*返回实体的所有键的集合*/
19             return entitydata.KeyProperties.Select(p => p.Name).ToArray();
20 
21         }
22         /// <summary>
23         /// 获得实体对应的表名
24         /// </summary>
25         /// <param name="ctx"></param>
26         /// <param name="entity"></param>
27         /// <returns></returns>
28         static string GetTableName(this DbContext ctx, Type entity)
29         {
30             var metadata = ((IObjectContextAdapter)ctx).ObjectContext.MetadataWorkspace;
31 
32             var storeItemCollection = metadata.GetItemCollection(DataSpace.SSpace);
33 
34             var entitySetBase = storeItemCollection.GetItems<EntityContainer>().Single().BaseEntitySets.Where(e => e.Name == entity.Name).Single();
35 
36             string tableName = entitySetBase.MetadataProperties["Schema"].Value + "." + entitySetBase.MetadataProperties["Table"].Value;
37 
38             return tableName;
39         }
40         /// <summary>
41         /// 获得实体的所有导航属性
42         /// </summary>
43         /// <param name="ctx"></param>
44         /// <param name="entity"></param>
45         /// <returns></returns>
46         static IEnumerable<PropertyInfo> GetNavigationPrpoperties(this DbContext ctx, Type entity)
47         {
48             var metadata = ((IObjectContextAdapter)ctx).ObjectContext.MetadataWorkspace;
49 
50             var entityType = metadata.GetItems(DataSpace.OSpace).Where(d => d.BuiltInTypeKind == BuiltInTypeKind.EntityType).OfType<EntityType>().Where(d => d.Name == entity.Name).Single();
51 
52             return (entityType.NavigationProperties.Select(d => entity.GetProperty(d.Name)).ToList());
53 
54         }
55     }
    View Code

     7、二级缓存【参考官方Second Level Cace for EntityFramework】

     1 　　public class EFConfiguration : DbConfiguration
 2     {
 3         public EFConfiguration()
 4         {
 5             var transactionHandler = new CacheTransactionHandler(new InMemoryCache());
 6 
 7             AddInterceptor(transactionHandler);
 8 
 9             var cachingPolicy = new CachingPolicy();
10 
11             Loaded +=
12              (sender, args) => args.ReplaceService<DbProviderServices>(
13              (s, _) => new CachingProviderServices(s, transactionHandler,
14               cachingPolicy));
15 
16         }
17 
18     }
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  • 原文地址：https://www.cnblogs.com/ziranquliu/p/4772384.html
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