The method used to create a DataView from a DataTable in ADO.NET is DataTable.DefaultView(). This method returns a DataView object representing a customized view of the DataTable, which can then be manipulated and used for various data operations such as sorting, filtering, and navigation. It provides a convenient way to work with subsets of data within a DataTable.

Common strategies for handling data conflicts in ADO.NET include implementing manual conflict resolution where the user is prompted to resolve conflicts, or automatic conflict resolution where predefined rules or custom logic resolve conflicts without user intervention.

An Entity Data Model (EDM) in LINQ to Entities represents the conceptual model of data in a database. It defines the structure of the data and the relationships between entities. EDM provides a higher-level abstraction over the database schema, allowing developers to work with entities and relationships rather than tables and columns directly.

Optimistic concurrency control is a strategy used in ADO.NET to handle data conflicts by assuming that conflicts are rare, thereby improving performance.

In hierarchical data, deferred loading techniques are employed to optimize performance by loading related data only when necessary, minimizing the amount of data retrieved from the database at once.

To implement a custom conflict resolution strategy in an ADO.NET application, you should handle the RowUpdating event. This event occurs before changes are sent to the database during an Update operation. By handling this event, you can examine the changes being made and implement your custom logic to resolve conflicts before they are applied to the database.

In LINQ to DataSet, the join clause is used to combine data from two or more data sources based on a related column between them. It allows you to perform operations similar to SQL joins, such as inner joins, outer joins, and cross joins, to retrieve and process data from multiple tables or collections simultaneously. Understanding how to use the join clause effectively is essential for querying and manipulating data using LINQ to DataSet.

In LINQ to DataSet, the GroupBy clause is used to group records based on a specified key. By grouping sales data by product category, you can then calculate the total revenue for each category. Thus, using GroupBy followed by an aggregation function like Sum allows you to achieve the task of calculating total revenue for each product category.

When interacting with an Oracle database in .NET applications, the appropriate data reader to use is the OracleDataReader. This specialized data reader is designed specifically for working with Oracle databases, providing efficient access to query results and handling Oracle-specific data types and features. Using the correct data reader ensures compatibility and optimal performance when retrieving data from an Oracle database.

Improving the performance of LINQ queries with multiple joins and filtering conditions involves using appropriate indexes on columns involved in joins and filters. This helps in optimizing data retrieval and processing, resulting in better query performance.