在C#.Net中，为DataTable设置了主键，但出现异常“Table没有主键”被抛出
确切的例外是 System.Data.dll 中发生“System.Data.MissingPrimaryKeyException”
附加信息：表没有主键。
不过我已经设置了主键。这是代码。谢谢。
DataColumn[] PrimaryKeyColumns; //Global
DataTable firstLinesDT = new DataTable();
column = new DataColumn();
column.DataType = System.Type.GetType("System.String");
column.ColumnName = "FirstLines";
column.Unique = true;
firstLinesDT.Columns.Add(column);
PrimaryKeyColumns = new DataColumn[1];
PrimaryKeyColumns[0] = column;
firstLinesDT.PrimaryKey = PrimaryKeyColumns;
column = new DataColumn();
column.DataType = System.Type.GetType("System.Int32");
column.ColumnName = "Length";
firstLinesDT.Columns.Add(column);
column = new DataColumn();
column.DataType = System.Type.GetType("System.String");
column.ColumnName = "FilePath";
firstLinesDT.Columns.Add(column);
**// EXCEPTION THROWN AT FIND OPERATION**
DataRow foundRow = firstLinesDT.NewRow();
foundRow = firstLinesDT.Rows.Find(line);
根据 msdn，这正是主键应该如何设置的- http://msdn.microsoft.com/en-us /library/system.data.datatable.primarykey.aspx
The precise exception is
'System.Data.MissingPrimaryKeyException' occurred in System.Data.dll
Additional information: Table doesn't have a primary key.
However, I have set the primary key. This is the code. Thanks.
DataColumn[] PrimaryKeyColumns; //Global
DataTable firstLinesDT = new DataTable();
column = new DataColumn();
column.DataType = System.Type.GetType("System.String");
column.ColumnName = "FirstLines";
column.Unique = true;
firstLinesDT.Columns.Add(column);
PrimaryKeyColumns = new DataColumn[1];
PrimaryKeyColumns[0] = column;
firstLinesDT.PrimaryKey = PrimaryKeyColumns;
column = new DataColumn();
column.DataType = System.Type.GetType("System.Int32");
column.ColumnName = "Length";
firstLinesDT.Columns.Add(column);
column = new DataColumn();
column.DataType = System.Type.GetType("System.String");
column.ColumnName = "FilePath";
firstLinesDT.Columns.Add(column);
**// EXCEPTION THROWN AT FIND OPERATION**
DataRow foundRow = firstLinesDT.NewRow();
foundRow = firstLinesDT.Rows.Find(line);
And according to msdn, this exactly how the primary key is supposed to be set-
http://msdn.microsoft.com/en-us/library/system.data.datatable.primarykey.aspx
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评论（3）
我遇到了同样的问题，PrimaryKey.Length 为 0，因为我在用适配器中的行填充
DataTable之前声明了主键数组。先尝试用数据填充它I had the same problem and PrimaryKey.Length was 0 because I was declaring the Primary keys array before I filled the
DataTablewith rows from the adapter. Try to fill it with data first我不是 100% 确定，但我相信在设置所有其他列之前您不会添加主键。
换句话说，将
firstLinesDT.PrimaryKey = PrimaryKeyColumns;移动到添加FilePath列的位置之后。I'm not 100% certain, but I believe you don't add the primary key until all of the other columns are set.
In other words move
firstLinesDT.PrimaryKey = PrimaryKeyColumns;to be after the point where you add theFilePathcolumn.我不知道这是否回答了您的问题，因为您的代码不包含
DataView，您可能将其遗漏，因为您认为它在示例中并不重要。但是，将表转换为 DataView，然后返回
ToTable()会删除 PrimaryKey。I don't know if this answers your question as your code does not include a
DataView, it's possible that you left it out as you didn't think it was important in the example.However, turning a table into a DataView, and then back
ToTable(), removes the PrimaryKey.