oracle 无法序列化数据表。未设置数据表名称
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Cannot serialize the DataTable. DataTable name is not set
提问by Nime Cloud
I need to export all datatables to individual XML files and I cannot export all the rows at once because of System.OutOfMemoryException if there is a huge table. So I tried to export N rows. However WriteXml throws an exception if I use paging syntax in query.
我需要将所有数据表导出到单独的 XML 文件，如果有一个巨大的表，我无法一次导出所有行，因为 System.OutOfMemoryException。所以我尝试导出 N 行。但是，如果我在查询中使用分页语法，WriteXml 会引发异常。
I've tested both queries in LINQPad, they are ok.
我已经在 LINQPad 中测试了这两个查询，它们没问题。
System.InvalidOperationException: Cannot serialize the DataTable. DataTable name is not set.
System.InvalidOperationException：无法序列化数据表。未设置数据表名称。
// The first query causes exception
string oraQueryGetTableData = "SELECT * FROM (SELECT t0.* FROM MY_TABLE t0) WHERE ROWNUM <= 100";
// The second query runs without any error
//oraQueryGetTableData = "SELECT * FROM MY_TABLE";
OracleCommand oraCommandGetTableData = new OracleCommand(oraQueryGetTableData, oraConnection);
OracleDataReader oraReaderTableData = oraCommandGetTableData.ExecuteReader();
DataTable dataTable = new DataTable();
dataTable.Load(oraReaderTableData);
// Exception might occur here
dataTable.WriteXml(writer, true);
What is the problem here or how can I fix this?
这里有什么问题或者我该如何解决这个问题？
回答by Jens Meinecke
As the exception says - the table does not have it's TableNameproperty set. So you just need to set it.
正如例外所说 - 该表没有TableName设置它的属性。所以你只需要设置它。
DataTable dataTable = new DataTable { TableName = "MyTableName"};
dataTable.Load(oraReaderTableData);
....
回答by Pranithan T.
If you use Newtonsoftto Deserialize the JSON string data to be DataTable, the TableNameattribute will NOTbe set. I composed the sample code and put the break point after the dtassignment to let you see what is dt.TableName. The debugging result is shown below:
如果您使用Newtonsoft将 JSON 字符串数据反序列化为DataTable，TableName则不会设置该属性。我编写了示例代码并在dt赋值之后放置了断点，让您看看dt.TableName. 调试结果如下图所示：
So, if you would like to return the DataTableas a result of web service method, the TableNameattribute assignment is needed after DeserializeObject. I change the code to be:
因此，如果您想返回DataTable作为 Web 服务方法的结果，TableName则需要在 之后进行属性分配DeserializeObject。我将代码更改为：
DataTable dt = JsonConvert.DeserializeObject<DataTable>(
@"[
{ col1: 'value1', col2: 'value2' },
{ col1: 'value3', col2: 'value4' },
{ col1: 'value5', col2: 'value6' },
]");
dt.TableName = "TableName";
And I debug it again. This is The preferable DataTablethat can be returned by a web method.
我再次调试它。这是DataTable可以通过 Web 方法返回的首选方法。
