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.

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.

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 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.

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

The significance of the CommandType property in an ADO.NET command object is that it determines the type of SQL command being executed. It can be set to CommandType.Text for regular SQL queries or CommandType.StoredProcedure for executing stored procedures.

You can execute a stored procedure in ADO.NET by creating a SqlCommand object with the stored procedure name and setting its CommandType property to StoredProcedure. Then, you can add parameters to the command if necessary and execute it using the ExecuteNonQuery method to perform operations that don't return data or ExecuteReader method to retrieve data. The ExecuteScalar method is used when the stored procedure returns a single value. The SqlDataAdapter is used for retrieving data into a DataSet, and SqlDataReader is used for reading data row by row.

LINQ to SQL is tightly coupled to SQL Server, whereas LINQ to Entities is more flexible and can work with various data sources beyond SQL Server, such as Oracle, MySQL, etc.

Data binding in DataGrid or DataGridView controls is crucial as it ensures that any modifications made to the underlying data are immediately reflected in the associated UI controls. This results in a more responsive and synchronized user interface, simplifying the development process and enhancing the overall user experience.

Connection pooling in ADO.NET offers better performance by reusing connections instead of creating new ones for each request. This reduces the overhead of establishing connections and can lead to significant performance improvements, especially in high-volume applications.

A stored procedure is a precompiled collection of one or more SQL statements which are stored in the database server. When you execute a stored procedure, you are actually running a precompiled execution plan, which can improve performance and security. They are commonly used to encapsulate complex business logic, enhance security by controlling access to data, and promote code reusability.

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.