ADO.Net数据库帮助类

 public  interface IDBHelper
    {
        /// <summary>
        /// 执行sql语句
        /// </summary>
        /// <param name="sql"></param>
        void ExecuteNonQuery(string sql, SqlParameter[] sqlParams = null);
        /// <summary>
        /// 执行sql返回单一结果 
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="sqlParams"></param>      
        object ExecuteScalar(string sql, SqlParameter[] sqlParams = null);       
        /// <summary>
        /// 事务执行sql
        /// </summary>
        /// <param name="sql"></param>
        void ExecuteTrans(string sql, SqlParameter[] sqlParams = null);
        /// <summary>
        /// 获取单个实体
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="id"></param>
        /// <returns></returns>      
        T QuerySingle<T>(T model,string tableName = null) where T : class, new();

        /// <summary>
        /// 查询数据表的全部数据
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <returns></returns>
        IEnumerable<T> QueryAll<T>(string tableName = null) where T : class, new();

        /// <summary>
        /// 插入实体
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="t"></param>
        /// <returns></returns>
        void Insert<T>(T model, string tableName = null) where T : class, new();

        /// <summary>
        /// 
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="list"></param>
        /// <returns></returns>
        void InsertList<T>(IEnumerable<T> list, string tableName = null) where T : class, new();
        /// <summary>
        /// 更新实体
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="t"></param>
        /// <returns></returns>
        void Update<T>(T model, string tableName = null) where T : class, new();

        /// <summary>
        /// 根据Id删除
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="id"></param>
        /// <returns></returns>
        void Delete<T>(T model, string tableName = null) where T : class, new();
    }

public class SQLHelper : IDBHelper
    {
        private string connString;

        public SQLHelper(string connString = null)
        {
            if(!string.IsNullOrEmpty(connString))
            {
                this.connString = connString;
            }
            else
            {
                this.connString = ConfigurationManager.ConnectionStrings["connString"].ToString();
            }           
        }

        #region 执行sql语句
        /// <summary>
        /// 执行sql语句
        /// </summary>
        /// <param name="sql"></param>
        public void ExecuteNonQuery(string sql, SqlParameter[] sqlParams = null)
        {
            using (SqlConnection conn = new SqlConnection(connString))
            {
                conn.Open();
                SqlCommand cmd = new SqlCommand(sql, conn);
                if (sqlParams != null)
                    cmd.Parameters.AddRange(sqlParams);
                cmd.ExecuteNonQuery();
            }
        }      
        /// <summary>
        /// 执行sql语句，返回单一结果
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public object ExecuteScalar(string sql, SqlParameter[] sqlParams = null)
        {
            using (SqlConnection conn = new SqlConnection(connString))
            {
                conn.Open();
                SqlCommand cmd = new SqlCommand(sql, conn);
                if (sqlParams != null)
                    cmd.Parameters.AddRange(sqlParams);
                return cmd.ExecuteScalar();
            }
        }     
        /// <summary>
        /// 事务执行sql
        /// </summary>
        /// <param name="sql"></param>
        public void ExecuteTrans(string sql, SqlParameter[] sqlParams = null)
        {
            SqlTransaction trans = null;
            try
            {
                using (SqlConnection conn = new SqlConnection(connString))
                {
                    conn.Open();
                    trans = conn.BeginTransaction();
                    SqlCommand cmd = new SqlCommand(sql, conn);
                    if (sqlParams != null)
                        cmd.Parameters.AddRange(sqlParams);
                    cmd.ExecuteNonQuery();
                    trans.Commit();
                }
            }
            catch (Exception ex)
            {
                if (trans != null && trans.Connection != null)
                    trans.Rollback();
                throw ex;
            }
        }      
        #endregion

        #region 根据实体增删改查
        /// <summary>
        /// 删除
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="model"></param>
        /// <param name="tableName"></param>
        /// <returns></returns>
        public void Delete<T>(T model, string tableName = null) where T : class, new()
        {
            Type type = typeof(T);
            if (type.GetProperty("Id") == null)
            {
                throw new ArgumentNullException(string.Format("实体{0}必须包含主键Id字段", type.Name));
            }
            string _tableName = GetTableName<T>(tableName);
            var Id = type.GetProperty("Id").GetValue(model);
            string txtSql = string.Format("Delete from [{0}] Where Id=@id", _tableName);
            ExecuteNonQuery(txtSql, new[] { new SqlParameter("@id", Id) });
        }
        /// <summary>
        /// 插入
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="model"></param>
        /// <param name="tableName"></param>
        /// <returns></returns>
        public void Insert<T>(T model, string tableName = null) where T : class, new()
        {            
            Type type = typeof(T);
            SqlParameter[] sqlParams = type.GetProperties().Where(p => p.Name != "Id").Select(s => new SqlParameter(string.Format("@{0}", s.Name), s.GetValue(model) ?? DBNull.Value)).ToArray();
            string txtSql = GetInsertSql(model, tableName);
            var result = ExecuteScalar(txtSql, sqlParams);
            var idProperty = type.GetProperty("Id");
            idProperty.SetValue(model,Convert.ChangeType(result, idProperty.PropertyType));//将插入生成的Id赋值给model

        }
        /// <summary>
        /// 插入多个实体
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="list"></param>
        /// <param name="tableName"></param>
        public void InsertList<T>(IEnumerable<T> list, string tableName = null) where T : class, new()
        {
            Type type = typeof(T);
            using (SqlConnection conn = new SqlConnection(connString))
            {
                conn.Open();
                foreach (var item in list)
                {
                    SqlParameter[] sqlParams = type.GetProperties().Where(p => p.Name != "Id").Select(s => new SqlParameter(string.Format("@{0}", s.Name), s.GetValue(item) ?? DBNull.Value)).ToArray();
                    string txtSql = GetInsertSql<T>(item, tableName);
                    SqlCommand cmd = new SqlCommand(txtSql, conn);
                    if (sqlParams != null)
                        cmd.Parameters.AddRange(sqlParams);
                    var result = cmd.ExecuteScalar();
                    var idProperty = type.GetProperty("Id");
                    idProperty.SetValue(item, Convert.ChangeType(result, idProperty.PropertyType));//将插入生成的Id赋值给model
                }         
            }          
        }
        /// <summary>
        /// 查询单个实体
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="model"></param>
        /// <param name="tableName"></param>
        /// <returns></returns>
        public T QuerySingle<T>(T model, string tableName = null) where T : class, new()
        {
            Type type = typeof(T);
            if (type.GetProperty("Id") == null)
            {
                throw new ArgumentNullException(string.Format("实体{0}必须包含主键Id字段", type.Name));
            }
            string _tableName = GetTableName<T>(tableName);
            var Id = type.GetProperty("Id").GetValue(model);
            string selectField = string.Join(",", type.GetProperties().Select(s => string.Format("[{0}]", s.Name)));
            string txtSql = string.Format("select {0} from [{1}] where Id =@id", selectField, _tableName);
            using (SqlConnection conn = new SqlConnection(connString))
            {
                conn.Open();
                SqlCommand cmd = new SqlCommand(txtSql, conn);
                cmd.Parameters.Add(new SqlParameter("@id",Id));
                SqlDataReader reader = cmd.ExecuteReader();
                return ReaderToEntity<T>(reader);
            }
        }
        /// <summary>
        /// 查询所有
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="tableName"></param>
        /// <returns></returns>
        public IEnumerable<T> QueryAll<T>(string tableName = null) where T : class, new()
        {
            Type type = typeof(T);
            string selectField = string.Join(",", type.GetProperties().Select(p => string.Format("[{0}]", p.Name)));
            string txtSql = string.Format("select {0} from [{1}]", selectField, type.Name);
            using (SqlConnection conn = new SqlConnection(connString))
            {
                conn.Open();
                SqlCommand cmd = new SqlCommand(txtSql, conn);
                SqlDataReader reader = cmd.ExecuteReader();
                return ReaderToList<T>(reader);
            }
        }
        /// <summary>
        /// 更新
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="model"></param>
        /// <param name="tableName"></param>
        public void Update<T>(T model, string tableName = null) where T : class, new()
        {
            Type type = typeof(T);
            if (type.GetProperty("Id") == null)
            {
                throw new ArgumentNullException(string.Format("实体{0}必须包含主键Id字段", type.Name));
            }
            string _tableName = GetTableName<T>(tableName);
            string setCloums = string.Join(",", type.GetProperties().Where(p => p.Name != "Id").Select(s => string.Format("[{0}]=@{0}", s.Name)));
            string txtSql = string.Format("update [{0}] set {1} where Id =@id",_tableName,setCloums);
            SqlParameter[] sqlParams = type.GetProperties().Select(s => new SqlParameter(string.Format("@{0}", s.Name), s.GetValue(model) ?? DBNull.Value)).ToArray();
            ExecuteNonQuery(txtSql, sqlParams);           
        }
        #endregion

        #region private
        private string GetTableName<T>(string tableName)
        {
            string result = tableName;
            if (string.IsNullOrEmpty(result))//如果参数tableName为空
            {
                //1.检查[tableName]属性
                Type type = typeof(T);
                var tableNameAttribute = (TableNameAttribute)type.GetCustomAttributes(typeof(TableNameAttribute), false).FirstOrDefault();
                if (tableNameAttribute != null)
                {
                    result = tableNameAttribute.TableName;
                }
                if (string.IsNullOrEmpty(result))
                {
                    //2.[tableName]属性为空 用实体名称
                    result = type.Name;
                }
            }
           
            return result;
        }

        private string GetInsertSql<T>(T model,string tableName)
        {
            Type type = typeof(T);
            if (type.GetProperty("Id") == null)
            {
                throw new ArgumentNullException(string.Format("实体{0}必须包含主键Id字段", type.Name));
            }
            string _tableName = GetTableName<T>(tableName);           
            string txtColums = string.Join(",", type.GetProperties().Where(p => p.Name != "Id").Select(s => string.Format("[{0}]", s.Name)));
            string txtValues = string.Join(",", type.GetProperties().Where(p => p.Name != "Id").Select(s => string.Format("@{0}", s.Name)));
            string txtSql = string.Format("insert into [{0}] ({1}) values({2});select @@identity;", _tableName, txtColums, txtValues);
            return txtSql;
        }
       
        private T ReaderToEntity<T>(SqlDataReader reader) where T : class, new()
        {
            T entity = new T();
            if (reader.Read())
            {
                Type type = typeof(T);
                foreach (var item in type.GetProperties())
                {
                    object oValue = reader[item.Name];
                    if (oValue is DBNull)
                    {
                        item.SetValue(entity, null);
                    }
                    else
                    {
                        item.SetValue(entity, oValue);
                    }
                }
            }
            return entity;
        }

        private IEnumerable<T> ReaderToList<T>(SqlDataReader reader) where T : class, new()
        {
            List<T> list = new List<T>();
            if (reader.Read())
            {
                Type type = typeof(T);
                do
                {
                    T entity = new T();
                    foreach (var item in type.GetProperties())
                    {
                        object oValue = reader[item.Name];
                        if (oValue is DBNull)
                        {
                            item.SetValue(entity, null);
                        }
                        else
                        {
                            item.SetValue(entity, oValue);
                        }
                    }
                    list.Add(entity);
                }
                while (reader.Read());
            }
            return list;
        }
        #endregion
    }