C#连接数据库是编写的SqlHelper

    static class SqlHelper  
        {  
            private static string connStr = ConfigurationManager.ConnectionStrings["dbConStr"].ConnectionString;  
      
            //封装方法的原则：把不变的放在方法里 变化的放到参数列表中  
            
            public static int ExecuteNonQuery(string sql,params SqlParameter[] parameters)  
            {  
                using (SqlConnection coon = new SqlConnection(connStr))  
                {  
                    coon.Open();  
                    using (SqlCommand cmd = coon.CreateCommand())  
                    {  
                        cmd.CommandText = sql;  
                        cmd.Parameters.AddRange(parameters);  
                        return cmd.ExecuteNonQuery();  
                    }  
                }  
            }  
      
            public static object ExecuteScalar(string sql,params SqlParameter[] parameters)  
            {  
                using (SqlConnection coon = new SqlConnection(connStr))  
                {  
                    coon.Open();  
                    using (SqlCommand cmd = coon.CreateCommand())  
                    {  
                        cmd.CommandText = sql;  
                        cmd.Parameters.AddRange(parameters);  
                        return cmd.ExecuteScalar();  
                    }  
                }  
            }  
      
             
            //由于查询的比较小  所以 可以直接用Table  
            public static DataTable ExecuteDataTable(string sql,params  SqlParameter[] parameters)  
            {  
                using (SqlConnection coon = new SqlConnection(connStr))  
                {  
                    coon.Open();  
                    using (SqlCommand cmd = coon.CreateCommand())  
                    {  
                        cmd.CommandText = sql;  
                        cmd.Parameters.AddRange(parameters);  
      
                        DataSet dataset = new DataSet();  
                        SqlDataAdapter adapter = new SqlDataAdapter(cmd);  
                        adapter.Fill(dataset);  
                        return dataset.Tables[0];  
                    }  
                }  
            }