No data exists for the row or column.

在数据库操作过程中读取数据有可能遇到标题所说的错误，解决方法：
如下代码，用红色的代码就会出现上述问题，这个时候需要捕获异常处理一下即可。

String conn = OracleHelper.DatabaseConnStr;
            String getConent = "SELECT 新闻内容,新闻来源 FROM xinwen WHERE SN =" + "'" + LabelZhuJian.Text + "'";
            OracleDataReader dr = OracleHelper.ExecuteReader(conn, CommandType.Text, getConent, null);
            while (dr.Read())
            {
                OracleLob myOracleClob = dr.GetOracleLob(0);
                StreamReader streamreader = new StreamReader(myOracleClob, Encoding.Unicode);
                char[] cbuffer = new char[1000000];
                while ((actual = streamreader.Read(cbuffer, 0, cbuffer.Length)) > 0)
                {
                    String content = new string(cbuffer, 0, actual);
                    this.FreeTextBoxXinWenNeiRong.Text = content;
                }

                //this.TextBoxXinWenLaiYuan.Text = dr.GetString(1);

                // 新闻来源 为空的需要异常处理
                try
                {
                    this.TextBoxXinWenLaiYuan.Text = dr.GetString(1);
                }
                catch (Exception ex)
                {
                    ex.ToString();
                    this.TextBoxXinWenLaiYuan.Text = "";
                }
                finally
                {
                    //
                }

            }
            dr.Close()