To get the primary key of a table through a DataTable

In many cases we need to know what the primary key of the table is. A table in Ado.net that a DataTable can map a database is provided. You can then take advantage of the DataTable's property PrimaryKey, which is the datacolumn[] type is an array. We can use the following code

Datacolumn[] cols;
cols = Table.primarykey;
Note that not cols are DataColumn arrays, not DataColumn variables. This is done primarily to address the problem of federated primary keys.
for (int i = 0; i < cols. Length; i++)
{
MessageBox.Show (Cols[i]. ColumnName);
}

The question has been settled, but cols. Length is 0. There was no information from the primary key that was taken from the database when the DataTable was populated by default. How do I get a primary key? The study found that when populating a dataset, you can use the DataAdapter MissingSchemaAction attribute to help us solve the problem, so we have the following code:

Populating a DataTable with DataAdapter
DataAdapter. MissingSchemaAction = MissingSchemaAction.AddWithKey;
DataAdapter. Fill (Table);

Datacolumn[] cols;
cols = Table.primarykey;
Note that not cols are DataColumn arrays, not DataColumn variables. This is done primarily to address the problem of federated primary keys.
for (int i = 0; i < cols. Length; i++)
{
MessageBox.Show (Cols[i]. ColumnName);
}

So we can get what we want. The MissingSchemaAction property is the action that needs to be performed to determine if an existing dataset (or DataTable) schema does not match the incoming data. MissingSchemaAction.AddWithKey is an enumeration value that is used to add the necessary column and primary key information to complete the schema, which allows the user to explicitly set the PRIMARY KEY constraint on each DataTable.