C#内置泛型委托之Func委托

using System.Runtime.CompilerServices; namespace System { // // 摘要: //     封装一个方法，该方法具有两个参数，并返回由 TResult 参数指定的类型的值。 // // 参数: //   arg1: //     此委托封装的方法的第一个参数。 // //   arg2: //     此委托封装的方法的第二个参数。 // // 类型参数: //   T1: //     此委托封装的方法的第一个参数的类型。 // //   T2: //     此委托封装的方法的第二个参数的类型。 // //   TResult: //     此委托封装的方法的返回值类型。 // // 返回结果: //     此委托封装的方法的返回值。 [TypeForwardedFrom("System.Core, Version=3.5.0.0, Culture=Neutral, PublicKeyToken=b77a5c561934e089")] public delegate TResult Func(T1 arg1, T2 arg2); }

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace FunDemo { class Program { static void Main(string[] args) { // 无参数，只要返回值 Func fun1 = new Func(FunWithNoPara); int result1= fun1(); Console.WriteLine(result1); Console.WriteLine("----------------------------"); Func fun2 = delegate { return 19; }; int result2 = fun2(); Console.WriteLine(result2); Console.WriteLine("----------------------------"); Func fun3 = () => { return 3; }; int result3 = fun3(); Console.WriteLine(result3); Console.WriteLine("----------------------------"); //有一个参数，一个返回值 Func fun4 = new Func(FunWithPara); int result4 = fun4(4); Console.WriteLine($"这里是一个参数一个返回值的方法，返回值是：{result4}"); Console.WriteLine("----------------------------"); // 使用委托 Func fun5 = delegate (int i) { return i.ToString(); }; string result5 = fun5(5); Console.WriteLine($"这里是一个参数一个返回值的委托，返回值是：{result5}"); Console.WriteLine("----------------------------"); // 使用匿名委托 Func fun6 = (int i) => { return i.ToString(); }; string result6 = fun6(6); Console.WriteLine($"这里是一个参数一个返回值的匿名委托，返回值是：{result6}"); Console.WriteLine("----------------------------"); // 多个输入参数 Func fun7 = new Func(FunWithMultiPara); bool result7 = fun7(2, "2"); Console.WriteLine($"这里是有多个输入参数的方法，返回值是：{result7}"); Console.WriteLine("----------------------------"); // 使用委托 Func fun8 = delegate (int i, string s) { return i.ToString().Equals(s) ? true : false; }; bool result8 = fun8(2, "abc"); Console.WriteLine($"这里是有多个输入参数的委托，返回值是：{result8}"); Console.WriteLine("----------------------------"); // 使用匿名委托 Func fun9 = (int i, string s) => { return i.ToString().Equals(s) ? true : false; }; bool result9 = fun9(45, "ert"); Console.WriteLine($"这里是有多个输入参数的匿名委托，返回值是：{result9}"); Console.ReadKey(); } static int FunWithNoPara() { return 10; } static int FunWithPara(int i) { return i; } static bool FunWithMultiPara(int i,string s) { return i.ToString().Equals(s) ? true : false; } } }

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace FunApplication.Model { public class BaseModel { public int Id { get; set; } } }

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace FunApplication.Model { public class Student : BaseModel { public string Name { get; set; } public int Age { get; set; } public int Sex { get; set; } public string Email { get; set; } } }

using FunApplication.Model; using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace FunApplication.IDAL { public interface IBaseDAL { T Query(int id) where T : BaseModel; List QueryAll() where T : BaseModel; int Insert(T t) where T : BaseModel; int Update(T t) where T : BaseModel; int Delete(int id) where T : BaseModel; } }

using System; using System.Collections.Generic; using System.Linq; using System.Reflection; using System.Text; using System.Threading.Tasks; namespace FunApplication.AttributeExtend { public static class AttributeHelper { public static string GetColumnName(this PropertyInfo prop) { if (prop.IsDefined(typeof(ColumnAttribute), true)) { ColumnAttribute attribute = (ColumnAttribute)prop.GetCustomAttribute(typeof(ColumnAttribute), true); return attribute.GetColumnName(); } else { return prop.Name; } } } }

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace FunApplication.AttributeExtend { [AttributeUsage(AttributeTargets.Property)] public class ColumnAttribute : Attribute { public ColumnAttribute(string name) { this._Name = name; } private string _Name = null; public string GetColumnName() { return this._Name; } } }

using FunApplication.IDAL; using FunApplication.Model; using System; using System.Collections.Generic; using System.Configuration; using System.Data.SqlClient; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Reflection; using FunApplication.AttributeExtend; namespace FunApplication.DAL { public  class BaseDAL : IBaseDAL { // 数据库链接字符串 private static string strConn = ConfigurationManager.ConnectionStrings["DbConnection"].ConnectionString; public  int Delete(int id) where T : BaseModel { int result = 0; using (SqlConnection conn = new SqlConnection(strConn)) { string strSQL = "delete from Student where Id=@Id"; SqlParameter para = new SqlParameter("Id", id); SqlCommand command = new SqlCommand(strSQL, conn); command.Parameters.Add(para); conn.Open(); result = command.ExecuteNonQuery(); } return result; } public int Insert(T t) where T : BaseModel { int result = 0; using (SqlConnection conn = new SqlConnection(strConn)) { Type type = typeof(T); var propArray = type.GetProperties().Where(p => p.Name != "Id"); string strSQL = "insert into Student Values (@Name,@Age,@Sex,@Email) "; SqlCommand command = new SqlCommand(strSQL, conn); var parameters = propArray.Select(p => new SqlParameter($"@{p.GetColumnName()}", p.GetValue(t) ?? DBNull.Value)).ToArray(); command.Parameters.AddRange(parameters); conn.Open(); result = command.ExecuteNonQuery(); } return result; } public T Query(int id) where T : BaseModel { Type type = typeof(T); string columnString = string.Join(",", type.GetProperties().Select(p => $"[{p.GetColumnName()}]")); string sql = $"SELECT {columnString} FROM [{type.Name}] WHERE Id={id}"; T t = null;// (T)Activator.CreateInstance(type); using (SqlConnection conn = new SqlConnection(strConn)) { SqlCommand command = new SqlCommand(sql, conn); conn.Open(); SqlDataReader reader = command.ExecuteReader(); List list = this.ReaderToList(reader); t = list.FirstOrDefault(); } return t; } public List QueryAll() where T : BaseModel { Type type = typeof(T); string columnString = string.Join(",", type.GetProperties().Select(p => $"[{p.GetColumnName()}]")); string sql = $"SELECT {columnString} FROM [{type.Name}] "; List list = new List(); using (SqlConnection conn = new SqlConnection(strConn)) { SqlCommand command = new SqlCommand(sql, conn); conn.Open(); SqlDataReader reader = command.ExecuteReader(); list = this.ReaderToList(reader); } return list; } public int Update(T t) where T : BaseModel { int result = 0; using (SqlConnection conn = new SqlConnection(strConn)) { Type type = typeof(T); var propArray = type.GetProperties().Where(p => p.Name != "Id"); string columnString = string.Join(",", propArray.Select(p => $"[{p.GetColumnName()}]=@{p.GetColumnName()}")); var parameters = propArray.Select(p => new SqlParameter($"@{p.GetColumnName()}", p.GetValue(t) ?? DBNull.Value)).ToArray(); //必须参数化  否则引号？  或者值里面还有引号 string strSQL = $"UPDATE [{type.Name}] SET {columnString} WHERE Id={t.Id}"; SqlCommand command = new SqlCommand(strSQL, conn); command.Parameters.AddRange(parameters); conn.Open(); result = command.ExecuteNonQuery(); } return result; } private List ReaderToList(SqlDataReader reader) where T : BaseModel { Type type = typeof(T); List list = new List(); while (reader.Read())//表示有数据  开始读 { T t = (T)Activator.CreateInstance(type); foreach (var prop in type.GetProperties()) { object oValue = reader[prop.GetColumnName()]; if (oValue is DBNull) oValue = null; prop.SetValue(t, oValue);//除了guid和枚举 } list.Add(t); } return list; } } }

using FunApplication.DAL; using FunApplication.Model; using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace FunApplication { class Program { static void Main(string[] args) { #region MyRegion BaseDAL dal = new BaseDAL(); // 查询 Student student = dal.Query(2); Console.WriteLine($"姓名：{student.Name},年龄：{student.Age},Email地址：{student.Email}"); Console.WriteLine("----------------------------"); // 查询所有 List list = dal.QueryAll(); Console.WriteLine($"集合个数：{list.Count}"); Console.WriteLine("----------------------------"); // 插入 Student studentIns = new Student() { Name = "小明", Age = 20, Sex = 2, Email = "xiaoming@qq.com" }; bool resultIns = dal.Insert(studentIns) > 0 ? true : false; Console.WriteLine($"插入执行结果：{resultIns}"); Console.WriteLine("----------------------------"); // 更新 Student studentUpd = new Student() { Id = 1, Name = "zhangsan1234", Age = 20, Sex = 2, Email = "zhangsan1234@qq.com" }; bool resultUpd = dal.Update(studentUpd) > 0 ? true : false; Console.WriteLine($"更新执行结果：{resultUpd}"); Console.WriteLine("----------------------------"); // 删除 bool resultDel = dal.Delete(3) > 0 ? true : false; Console.WriteLine($"删除执行结果：{resultDel}"); #endregion Console.ReadKey(); } } }

using FunApplication.AttributeExtend; using FunApplication.IDAL; using FunApplication.Model; using System; using System.Collections.Generic; using System.Configuration; using System.Data; using System.Data.SqlClient; using System.Linq; using System.Reflection; using System.Text; using System.Threading.Tasks; namespace FunApplication.DAL { public class FunBaseDAL : IBaseDAL { // 数据库链接字符串 private static string strConn = ConfigurationManager.ConnectionStrings["DbConnection"].ConnectionString; public int Delete(int id) where T : BaseModel { Type type = typeof(T); string sql = $"delete from {type.Name} where Id=@Id"; Func func = (SqlCommand command) => { SqlParameter para = new SqlParameter("Id", id); command.Parameters.Add(para); return command.ExecuteNonQuery(); }; return ExcuteSql(sql, func); } public int Insert(T t) where T : BaseModel { int result = 0; Type type = typeof(T); var propArray = type.GetProperties().Where(p => p.Name != "Id"); string strSQL = "insert into Student Values (@Name,@Age,@Sex,@Email) "; var parameters = propArray.Select(p => new SqlParameter($"@{p.GetColumnName()}", p.GetValue(t) ?? DBNull.Value)).ToArray(); Func func = (SqlCommand command) => { command.Parameters.AddRange(parameters); return command.ExecuteNonQuery(); }; result = ExcuteSql(strSQL, func); return result; } public T Query(int id) where T : BaseModel { Type type = typeof(T); string columnString = string.Join(",", type.GetProperties().Select(p => $"[{p.GetColumnName()}]")); string sql = $"SELECT {columnString} FROM [{type.Name}] WHERE Id=@Id"; T t = null; DataTable dt = new DataTable(); Func func = (SqlCommand command) => { SqlParameter para = new SqlParameter("@Id", id); command.Parameters.Add(para); SqlDataAdapter adapter = new SqlDataAdapter(command); //SqlDataReader reader = command.ExecuteReader(); //List list = this.ReaderToList(reader); adapter.Fill(dt); List list = ConvertToList(dt); T tResult = list.FirstOrDefault(); return tResult; }; t = ExcuteSql(sql, func); return t; } public List QueryAll() where T : BaseModel { Type type = typeof(T); string columnString = string.Join(",", type.GetProperties().Select(p => $"[{p.GetColumnName()}]")); string sql = $"SELECT {columnString} FROM [{type.Name}] "; T t = null; Func> func = (SqlCommand command) => { SqlDataReader reader = command.ExecuteReader(); List list = this.ReaderToList(reader); return list; }; return ExcuteSql>(sql, func); } public int Update(T t) where T : BaseModel { int result = 0; Type type = typeof(T); var propArray = type.GetProperties().Where(p => p.Name != "Id"); string columnString = string.Join(",", propArray.Select(p => $"[{p.GetColumnName()}]=@{p.GetColumnName()}")); var parameters = propArray.Select(p => new SqlParameter($"@{p.GetColumnName()}", p.GetValue(t) ?? DBNull.Value)).ToArray(); //必须参数化  否则引号？  或者值里面还有引号 string strSQL = $"UPDATE [{type.Name}] SET {columnString} WHERE Id={t.Id}"; Func func = (SqlCommand command) => { command.Parameters.AddRange(parameters); return command.ExecuteNonQuery(); }; result = ExcuteSql(strSQL, func); return result; } //多个方法里面重复对数据库的访问  想通过委托解耦，去掉重复代码 private T ExcuteSql(string sql, Func func) { using (SqlConnection conn = new SqlConnection(strConn)) { using (SqlCommand command = new SqlCommand(sql, conn)) { conn.Open(); SqlTransaction sqlTransaction = conn.BeginTransaction(); try { command.Transaction = sqlTransaction; T tResult = func.Invoke(command); sqlTransaction.Commit(); return tResult; } catch (Exception ex) { sqlTransaction.Rollback(); throw; } } } } private List ReaderToList(SqlDataReader reader) where T : BaseModel { Type type = typeof(T); List list = new List(); while (reader.Read())//表示有数据  开始读 { T t = (T)Activator.CreateInstance(type); foreach (var prop in type.GetProperties()) { object oValue = reader[prop.GetColumnName()]; if (oValue is DBNull) oValue = null; prop.SetValue(t, oValue);//除了guid和枚举 } list.Add(t); } reader.Close(); return list; } } }

using FunApplication.DAL; using FunApplication.Model; using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace FunApplication { class Program { static void Main(string[] args) { #region 传统实现 //BaseDAL dal = new BaseDAL(); //// 查询 //Student student = dal.Query(2); //Console.WriteLine($"姓名：{student.Name},年龄：{student.Age},Email地址：{student.Email}"); //Console.WriteLine("----------------------------"); //// 查询所有 //List list = dal.QueryAll(); //Console.WriteLine($"集合个数：{list.Count}"); //Console.WriteLine("----------------------------"); //// 插入 //Student studentIns = new Student() //{ //    Name = "小明", //    Age = 20, //    Sex = 2, //    Email = "xiaoming@qq.com" //}; //bool resultIns = dal.Insert(studentIns) > 0 ? true : false; //Console.WriteLine($"插入执行结果：{resultIns}"); //Console.WriteLine("----------------------------"); //// 更新 //Student studentUpd = new Student() //{ //    Id = 1, //    Name = "zhangsan1234", //    Age = 20, //    Sex = 2, //    Email = "zhangsan1234@qq.com" //}; //bool resultUpd = dal.Update(studentUpd) > 1 ? true : false; //Console.WriteLine($"更新执行结果：{resultUpd}"); //Console.WriteLine("----------------------------"); //// 删除 //bool resultDel = dal.Delete(5) > 1 ? true : false; //Console.WriteLine($"删除执行结果：{resultDel}"); #endregion #region 利用委托 // 查询 FunBaseDAL dal = new FunBaseDAL(); Student student = dal.Query(1); Console.WriteLine($"姓名：{student.Name},年龄：{student.Age},Email地址：{student.Email}"); Console.WriteLine("----------------------------"); // 查询所有 List list = dal.QueryAll(); Console.WriteLine($"集合个数：{list.Count}"); Console.WriteLine("----------------------------"); // 插入 Student studentIns = new Student() { Name = "tom", Age = 19, Sex = 1, Email = "tom@163.com" }; bool resultIns = dal.Insert(studentIns) > 0 ? true : false; Console.WriteLine($"插入执行结果：{resultIns}"); Console.WriteLine("----------------------------"); List list1 = dal.QueryAll(); Console.WriteLine($"插入后集合个数：{list1.Count}"); Console.WriteLine("----------------------------"); // 更新 Student studentUpd = new Student() { Id = 2, Name = "马六123", Age = 20, Sex = 2, Email = "maliu1234@qq.com" }; bool resultUpd = dal.Update(studentUpd) > 0 ? true : false; Console.WriteLine($"更新执行结果：{resultUpd}"); Console.WriteLine("----------------------------"); // 删除 bool resultDel = dal.Delete(8) > 0 ? true : false; Console.WriteLine($"删除执行结果：{resultDel}"); List list2 = dal.QueryAll(); Console.WriteLine($"删除后集合个数：{list2.Count}"); Console.WriteLine("----------------------------"); #endregion Console.ReadKey(); } } }

/// 
 /// 将DataTable转换成List /// 
 ///  ///  ///  private List ConvertToList(DataTable dt) where T:BaseModel { Type type = typeof(T); List list = new List(); foreach(DataRow dr in dt.Rows) { T t = (T)Activator.CreateInstance(type); foreach(PropertyInfo prop in type.GetProperties()) { object value = dr[prop.GetColumnName()]; if(value is DBNull) { value = null; } prop.SetValue(t, value); } list.Add(t); } return list; }