反射实例--反射，泛型，委托实现简单的增删查

一、打开VS2017，新建一个控制台项目：ReflactionDemo1

 

二、新建类库：ReflactionDemo1.Model  

1.在类库下面新建抽象类：BaseModel.cs 　　

public abstract class BaseModel
{
        [PrimaryKey("ID")]
        public virtual int ID { get; set; }
}

2.新建实体类：Students.cs  并且继承：BaseModel.cs

public class Students : BaseModel
{
        public string Name { get; set; }
        public int Age { get; set; }
        public string Address { get; set; }
}

3.新建特性扩展类：PrimaryKeyAttribute.cs  用于过滤主键ID

[AttributeUsage(AttributeTargets.Property, Inherited = false, AllowMultiple = false)]
public class PrimaryKeyAttribute : Attribute
{
        public PrimaryKeyAttribute(string keyName)
        {
            KeyName = keyName;
        }
        public string KeyName { get; set; }
}

 

三、新建类库：ReflactionDemo1.IDBSqlserver

1.新建接口：IDbHelper.cs   并添加增删查等方法体

public interface IDbHelper
{
        bool Add<T>(T t) where T : BaseModel;
        T Get<T>(int Id) where T: BaseModel;
        bool Delete<T>(int id) where T : BaseModel;
        List<T> GetList<T>() where T : BaseModel;
}

四、新建类库：ReflactionDemo1.DBSqlserver

1.新建类：DbHelper.cs 用于继承接口：IDbHelper.cs ，并实现接口的方法

public class DbHelper : IDbHelper
    {
        private static string connectionString = ConfigurationManager.AppSettings["ConnectionString"];

        public bool Add<T>(T t) where T : BaseModel
        {
            var type = typeof(T);
            var properties = type.GetProperties().Where(s => !s.GetCustomAttributes(typeof(PrimaryKeyAttribute)).Any()).ToList();
            var columnsName = string.Join(",", properties.Select(s => s.Name));
            var columnsParameters = string.Join(",", properties.Select(s => $"@{s.Name}"));
            var parameters = new List<SqlParameter>(properties.Select(s => new SqlParameter($"@{s.Name}", s.GetValue(t))));
            string sql = $"INSERT INTO [{type.Name}]({columnsName}) VALUES({columnsParameters})";
            return ExecuteSql(sql, cmd =>
            {
                foreach (var parameter in parameters)
                {
                    cmd.Parameters.Add(parameter);
                }
                return cmd.ExecuteNonQuery() > 0;
            });
        }

        public bool Delete<T>(int id) where T : BaseModel
        {
            var type = typeof(T);
            string sql = $"delete from [{type.Name}] where id={id}";
            return ExecuteSql(sql, cmd =>
            {
                return cmd.ExecuteNonQuery() > 0;
            });
        }

        public T ExecuteSql<T>(string sql, Func<IDbCommand, T> func)
        {
            using (SqlConnection conn = new SqlConnection(connectionString))
            {
                conn.Open();
                IDbCommand cmd = conn.CreateCommand();
                cmd.CommandText = sql;
                cmd.CommandType = CommandType.Text;
                return func(cmd);
            }
        }

        public T Get<T>(int Id) where T : BaseModel
        {
            var t = Activator.CreateInstance<T>();
            var type = typeof(T);
            var properties = type.GetProperties().ToList();
            var columnsName = string.Join(",", properties.Select(s => s.Name));
            string sql = $"SELECT {columnsName} FROM [{type.Name}] WHERE id={Id}";
            return ExecuteSql(sql,cmd =>
            {
                IDataReader reader = cmd.ExecuteReader();
                while (reader.Read())
                {
                    SetProperties(properties, reader, t);
                }
                return t;
            });
        }

        public List<T> GetList<T>() where T : BaseModel
        {
            List<T> list = new List<T>();
            var type = typeof(T);
            var properties = type.GetProperties().ToList();
            var columnsName = string.Join(",", properties.Select(s => s.Name));
            string sql = $"SELECT {columnsName} FROM [{type.Name}]";
            return ExecuteSql(sql,cmd =>
            {
                IDataReader reader = cmd.ExecuteReader();
                while (reader.Read())
                {
                    var t = Activator.CreateInstance<T>();
                    SetProperties(properties, reader, t);
                    list.Add(t);
                }
                return list;
            });
        }

        private static void SetProperties<T>(List<PropertyInfo> properties, IDataReader reader, T t)
        {
            foreach (var property in properties)
            {
                if (reader[property.Name] != DBNull.Value)
                {
                    property.SetValue(t, reader[property.Name]);
                }
            }
        }

五、在控制台程序ReflactionDemo1

1.在App.config 配置文件里面配置

  <appSettings>
    <!--程序集配置-->
    <add key="DbConfig" value="ReflactionDemo1.DBSqlserver,ReflactionDemo1.DBSqlserver.DbHelper"/>
    <!--数据库字符串连接-->
    <add key="ConnectionString" value="Server=DESKTOP-6IQUA2VFMM;Database=School;User ID=sa;Password=123456;"/>
  </appSettings>

2.新建类：SimpleFactory.cs  用于实现反射动态创建实例

public class SimpleFactory
{
        public static string dllName = ConfigurationManager.AppSettings["DbConfig"].Split(',')[0];
        public static string typeName= ConfigurationManager.AppSettings["DbConfig"].Split(',')[1];
        public static IDbHelper CreateInstance()
        {
            Assembly assembly = Assembly.Load(dllName);
            var type = assembly.GetType(typeName);
            var o = Activator.CreateInstance(type);
            return (IDbHelper)o;
        }
}

六、在控制台调用方法测试

class Program
{
        static void Main(string[] args)
        {
            IDbHelper dbHelper = SimpleFactory.CreateInstance();
            Students student = new Students
            {
                Address = "测试",
                Age = 20,
                Name = "admin"
            };
            var model = dbHelper.Add<Students>(student);
        }
}