表属性破坏后C＃键入DataSet Copy（） [英] Table Property broken after C# Typed DataSet Copy()

问题描述

我有一个类型化的数据集，我想要复制多个表，数据和模式。我可以访问我原来的表：

  MyDataSetType dsMyFirstDataSet; 
 MyDataTableType dtTable1; 
 MyDataTableType dtTable2; 
 
 dtTable1 = dsMyFirstDataSet.MeaningfulTableName1; 
 dtTable2 = dsMyFirstDataSet.MeaningfulTableName2; 
  

当我执行以下操作时，我无法再通过新版本的名称访问表，我可以通过Tables集合。

  MyDataSetType dsMySecondDataSet; 
 dsMySecondDataSet = dsMyFirstDataSet.Copy（）; 
 
 dtTable1 = dsMySecondDataSet.MeaningfulTableName1; // null 
 dtTable2 = dsMySecondDataSet.MeaningfulTableName2; // null 
 
 dtTable1 = dsMySecondDataSet.Tables [0]; // table not null / copied ok 
 dtTable2 = dsMySecondDataSet.Tables [1]; // table not null / copied ok 
  

我正在通过索引访问它们，如第二个例子但我想知道为什么命名表链接被切断了？我必须编写自己的Copy（）方法来保留对表的命名访问吗？

解决方案

我的猜测是，你的调用复制返回一个非类型的DataSet（虽然我不知道为什么你不会得到编译器错误）。

尝试更改您调用的行将复制到此：

  dsMySecondDataSet =（MyDataSetType）dsMyFirstDataSet.Copy（）; 
  

I've got a typed DataSet with multiple tables that I want copy, complete with data as well as schema. I can access the tables like so in my original:

MyDataSetType dsMyFirstDataSet;
MyDataTableType dtTable1;
MyDataTableType dtTable2;

dtTable1 = dsMyFirstDataSet.MeaningfulTableName1;
dtTable2 = dsMyFirstDataSet.MeaningfulTableName2;

When I do the following, I can no longer access the tables via the names in the new version but I can via the Tables collection.

MyDataSetType dsMySecondDataSet; 
dsMySecondDataSet = dsMyFirstDataSet.Copy();

dtTable1 = dsMySecondDataSet.MeaningfulTableName1;  // null
dtTable2 = dsMySecondDataSet.MeaningfulTableName2;  // null

dtTable1 = dsMySecondDataSet.Tables[0];  // table not null/copied ok
dtTable2 = dsMySecondDataSet.Tables[1];  // table not null/copied ok

I'm currently accessing them via the index like the second example but I'm wondering why the named table link has been severed? Do I have to write my own Copy() method to preserve the named access to the tables?

解决方案

My guess is that your call to Copy is returning a non-typed DataSet (though I'm not sure why you wouldn't get a compiler error).

Try changing the line where you call Copy to this:

dsMySecondDataSet = (MyDataSetType) dsMyFirstDataSet.Copy();

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