简单的SqlHelper

public class SqlHelper
    {
        public static string connstr= ConfigurationManager.ConnectionStrings["Connstr"].ConnectionString;

        /// <summary>
        /// 执行增删改
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="parameters"></param>
        /// <returns></returns>
        public static int ExecuteNonQuery(string sql, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connstr))
            {
                conn.Open();
                using (SqlCommand cmd = new SqlCommand())
                {
                    cmd.Connection = conn;
                    cmd.CommandText = sql;
                    cmd.Parameters.AddRange(parameters);
                    return cmd.ExecuteNonQuery();
                }
            }
        }

        /// <summary>
        /// 返回之后一行一列的数据
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="parameters"></param>
        /// <returns></returns>
        public static object ExecuteScalar(string sql, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connstr))
            {
                conn.Open();
                using (SqlCommand cmd = new SqlCommand())
                {
                    cmd.Connection = conn;
                    cmd.CommandText = sql;
                    cmd.Parameters.AddRange(parameters);
                    return cmd.ExecuteScalar();
                }
            }
        }

        /// <summary>
        /// 返回查询的表
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="parameters"></param>
        /// <returns></returns>
        public static DataTable ExecuteDataTable(string sql, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connstr))
            {
                conn.Open();
                using (SqlCommand cmd = new SqlCommand())
                {
                    cmd.Connection = conn;
                    cmd.CommandText = sql;
                    cmd.Parameters.AddRange(parameters);
                    SqlDataAdapter ada = new SqlDataAdapter(cmd);
                    DataSet ds = new DataSet();
                    ada.Fill(ds);
                    return ds.Tables[0];
                }
            }
        }

        /// <summary>
        /// 从数据库查询的数据，如果是DBNull就转换成null
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
        public static object FromDBNull(object value)
        {
            if (value == DBNull.Value)
            {
                return null;
            }
            else
            {
                return value;
            }
        }

        /// <summary>
        /// 把数据插入数据库中，如果是null就转换成DBNull
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
        public static object ToDBNull(object value)
        {
            if (value == null)
            {
                return DBNull.Value;
            }
            else
            {
                return value;
            }
        }

这是简单的sqlHelper，保存一下。