SqlHelper模板

在实际开发中，我们不会直接使用拼写SQL语句的方法进行数据库操作，而是使用参数化的方法进行数据库操作，这样做的好处很多，不仅提高了程序的健壮性，同时也避免的SQL注入的问题。在这里，笔者为初学者提供一个SQLHelper模板，希望对新手有所启发。

public static class SqlHelper
{
    public static readonly string strConn = ConfigurationManager.ConnectionStrings["strConn"].ConnectionString;

    public static int ExecuteNonQuery(string cmdText, params SqlParameter[] parameters)
    {
        using (SqlConnection conn = new SqlConnection(strConn))
        {
            conn.Open();
            return ExecuteNonQuery(conn, cmdText, parameters);
        }
    }
    public static int ExecuteNonQuery(SqlConnection conn, string cmdText, params SqlParameter[] parameters)
    {
        using (SqlCommand cmd = conn.CreateCommand())
        {
            cmd.CommandText = cmdText;
            cmd.Parameters.AddRange(parameters);
            return cmd.ExecuteNonQuery();
        }
    }

    public static object ExecuteScalar(string cmdText, params SqlParameter[] parameters)
    {
        using (SqlConnection conn = new SqlConnection(strConn))
        {
            conn.Open();
            return ExecuteScalar(conn, cmdText, parameters);
        }
    }
    public static object ExecuteScalar(SqlConnection conn, string cmdText, params SqlParameter[] parameters)
    {
        using (SqlCommand cmd = conn.CreateCommand())
        {
            cmd.CommandText = cmdText;
            cmd.Parameters.AddRange(parameters);
            return cmd.ExecuteScalar();
        }
    }

    public static DataTable ExecuteDataTable(string cmdText, params SqlParameter[] parameters)
    {
        using (SqlConnection conn = new SqlConnection(strConn))
        {
            conn.Open();
            return ExecuteDataTable(conn, cmdText, parameters);
        }
    }
    public static DataTable ExecuteDataTable(SqlConnection conn, string cmdText, params SqlParameter[] parameters)
    {
        using (SqlCommand cmd = conn.CreateCommand())
        {
            cmd.CommandText = cmdText;
            cmd.Parameters.AddRange(parameters);
            using (SqlDataAdapter adapter = new SqlDataAdapter(cmd))
            {
                DataTable dt = new DataTable();
                adapter.Fill(dt);
                return dt;
            }
        }
    }

    /// <summary>
    /// 存数据时防止为空
    /// </summary>
    /// <param name="value"></param>
    /// <returns></returns>
    public static object ToDbValue(this object value)
    {
        return value == null ? DBNull.Value : value;
    }

    /// <summary>
    /// 取数据时防止为空
    /// </summary>
    /// <param name="value"></param>
    /// <returns></returns>
    public static object FromDbValue(this object value)
    {
        return value == DBNull.Value ? null : value;
    }
}