如何在创建后将 VB.NET DataTable Column 定义为主键
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How to define a VB.NET DataTable Column as primary key after creation
提问by Olga
I am importing Tables from a Oracle DataBase, using a VB.NET dataAdapter. I use the "fill" command to add the imported data to a DataSet. How is it possible to define a specific column of a DataTable as PrimaryKey, after the DataTable is already filled with data?
我正在使用 VB.NET dataAdapter 从 Oracle 数据库导入表。我使用“fill”命令将导入的数据添加到数据集。在 DataTable 已经填充了数据之后，如何将 DataTable 的特定列定义为 PrimaryKey？
采纳答案by Rob
You can set the primary key of a table by:
您可以通过以下方式设置表的主键：
Dim table As New DataTable()
table.Columns.Add(New DataColumn("MyColumn"))
Dim primaryKey(1) As DataColumn
primaryKey(1) = table.Columns("MyColumn")
table.PrimaryKey = primaryKey
To be able to use the primary key, you need to ensure that all values for the given column are unique.
为了能够使用主键，您需要确保给定列的所有值都是唯一的。
I primarily work in C# and have a couple of Extension methods I use to "tidy" the calls I need to make, which you might want to consider translating to VB and using:
我主要在 C# 中工作，并且有几个扩展方法用于“整理”我需要进行的调用，您可能需要考虑将其转换为 VB 并使用：
public static void SetPrimaryKey(this DataTable value, string columnName)
{
value.PrimaryKey = new DataColumn[] { value.Columns[columnName] };
}
public static DataRow FindByPrimaryKey(this DataTable value, object key)
{
return value.Rows.Find(key);
}
// I can then do:
DataTable table = CallToRoutineThatGetsMyDataTable();
table.SetPrimaryKey("PKColumnName");
DataRow result = table.FindByPrimaryKey("valueToFindWith");
回答by Kleinux
As long as the values in the column are unique
只要列中的值是唯一的
table.PrimaryKey = new DataColumn[] { table.Columns["Id"] };
adjust for your column names.
调整您的列名。
回答by Matt Roy
Here is a one-liner in VB (the question was with "using VB.NET"). This example is with 2 columns indexed:
这是 VB 中的一个单行（问题是“使用 VB.NET”）。这个例子有 2 列索引：
table.PrimaryKey = New DataColumn() {table.Columns("column1"), _
table.Columns("column2")}
Update:And here's another one-liner on how to use this 2 columns index to find a row:
更新：这是关于如何使用这 2 列索引查找行的另一个单行：
table.Rows.Find(New Object() {value1, value2}) '<- DataRow returned
回答by CHale
Thanks for the answer Rob - there is a slight issue with the vb version though as the index should be zero-based:
感谢 Rob 的回答 - vb 版本有一个小问题，尽管索引应该是从零开始的：
Dim table As New DataTable()
table.Columns.Add(New DataColumn("MyColumn"))
Dim primaryKey(1) As DataColumn
primaryKey(0) = table.Columns("MyColumn")
table.PrimaryKey = primaryKey
