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This article introduces the relevant knowledge of "what is the relevant knowledge of ADO.NET collection?" in the operation of actual cases, many people will encounter such a dilemma, and then let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

If the data provider is a database management system (DBMS), the content of the property is likely to be the SQL command string. When the Update method executes, if these properties are not set, but the DataSet object contains primary key information, the ADO.NET collection automatically generates command text.

DataRow: to populate a table, we can use the automatic data binding capabilities of the command, or we can add rows manually by creating a DataRow object, inserting a DataRow object into the table, and then filling in the data for each field of the record. We can navigate the elements of the DataTable through the Rows collection, implement a sequential navigator using the Rows collection, or jump to a specific record by searching or directly locating.

DataRelation: this object represents the parent-child relationship between two tables. The relationship is based on columns of the same data type, but the columns do not have to have the same accuracy. The relationship can be an ADO.NET set, an one-to-many (1-to-many) or many-to-many (MRV N) relationship. Relationships can easily propagate changes to parent records to child records, but this is not the default behavior.

To enable the DataRelation object, the ADO.NET collection we must add a ForeignKeyConstraint to the ConstraintsCollection member of the data table to be modified. The ConstraintsCollection member of the DataTable object determines what actions to take when the value of a parent table is deleted or changed.

Once the relationship is set, ADO.NET rejects all dataset changes that break the relationship and generates a run-time exception. When traversing the records of a table, call the GetChildRows method to access all related rows from the connected table. The GetChildRows method returns an array of DataRow objects, the ADO.NET collection, which is a new hierarchical record navigation method, while the traditional record navigation mode belongs to sequential mode or random mode.

Relationships are not transmissible. Suppose table An is associated with table B, which in turn is associated with some rows of table C. In addition, suppose that when traversing table A records, for each table A record, we want to access the child records in the existing relationship. If we want to access Table C records that correspond to specific records in Table B, we cannot use the DataRow object of Table B obtained from the relationship of AME B

Instead, we must open a new table view from Table B, find the specific record we want, and the ADO.NET collection then calls the GetChildRows method on Table C's relationship through Table B.

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