The IsLoaded() method is used when using explicit loading in Entity Framework to check if related data is already loaded. This method returns true if the related data is already loaded and false otherwise. This helps in avoiding unnecessary loading of related entities and ensures efficient use of database resources. Explicit loading is a technique used to load related entities explicitly when needed.

Deferred loading is crucial in scenarios with disconnected entities to prevent unintended data retrieval from the database. In disconnected scenarios, you typically load entities, detach them from the context, and then work with them. Deferred loading allows you to delay the loading of related entities until they are explicitly requested, helping to optimize performance and reduce unnecessary data retrieval.

Dynamic Proxies are used by Entity Framework to enable lazy loading. Lazy loading is a technique where related objects are automatically loaded from the database when you access a navigation property. Dynamic Proxies are generated by Entity Framework to enable lazy loading behavior for entity types.

The correct method to determine the number of non-null values in a column is Count(). Count() counts the number of elements in a sequence that satisfy a condition, in this case, being non-null. Sum() calculates the total sum of numeric values in a column. Average() calculates the average value of a numeric column. Max() returns the maximum value in a column.

In Entity Framework, aggregate functions can be used in conjunction with the GroupBy clause. This allows for grouping data based on certain criteria and then performing aggregate calculations on each group. The GroupBy method is used to group the data, and then aggregate functions like SUM, AVG, etc., can be applied to each group individually. This process enables complex data analysis and reporting in Entity Framework.

In Entity Framework, aggregate functions like SUM, AVG, COUNT, etc., handle nullable properties by ignoring null values. This means that when computing an aggregate function, Entity Framework excludes null values from the calculation. This behavior helps in obtaining accurate results when dealing with nullable properties in queries.

The correct option is "Sum calculates the sum of values in a specified column, whereas Aggregate can perform various aggregate functions such as sum, average, minimum, maximum, and more." The Sum method in Entity Framework specifically calculates the sum of values in a specified column, while the Aggregate method is more versatile and allows for performing various aggregate functions beyond just summing values. Aggregate can handle complex scenarios where you might need to compute multiple aggregations simultaneously or apply custom logic during aggregation.

The correct option is "Max." In Entity Framework, you can use the Max function to return a single value representing the maximum value of a specified column. This function is particularly useful when you need to find the maximum value of a specific property across all entities in a DbSet. For example, you might use the Max function to find the maximum salary or the maximum age among a collection of entities.

The correct option is "Min." The Min function in Entity Framework is used to find the minimum value of a property across all entities in a DbSet. It retrieves the smallest value of the specified property from the entities in the DbSet. This function is useful when you need to find the smallest value of a particular property, such as the minimum age or the minimum salary in a collection of entities.

The Count method in Entity Framework is used to determine the total number of entities present within a DbSet or query result set. It simply returns the count of entities without considering any specific property.

The Sum method in Entity Framework is used to calculate the total sum of a numeric column within a dataset or query result set. It is particularly useful for calculating the total monetary value, quantity, or any other numerical aggregation.

The correct option is "Aggregate". After using GroupBy in Entity Framework, Aggregate method is applied to perform calculations on each group. It's used for calculating aggregates like sum, average, etc.