LINQ - filter child collection

LINQ - filter child collection

To filter a child collection using LINQ, you can use the Where method along with a lambda expression. Here's an example to illustrate this:

Let's say you have two classes: Parent and Child, where Parent has a collection of Child objects:

public class Parent { public int Id { get; set; } public string Name { get; set; } public List<Child> Children { get; set; } } public class Child { public int Id { get; set; } public string Name { get; set; } }

To filter the Children collection based on a condition, you can use LINQ as follows:

var parents = dbContext.Parents .Where(p => p.Children.Any(c => c.Name == "John")) .ToList();

In this example, dbContext is your instance of the Entity Framework's DbContext class, and Parents is the DbSet representing your parent entities.

The Where method is used to filter the parent entities based on a condition. The condition p.Children.Any(c => c.Name == "John") checks if any child object in the Children collection has a Name property equal to "John". Only parents that have at least one child with the name "John" will be included in the result.

Calling ToList() executes the query and returns a list of parent objects that satisfy the filtering condition.

You can modify the condition inside the Where method to suit your specific filtering requirements, such as checking for a specific property value, using comparison operators, or combining multiple conditions.

Examples

  1. LINQ filter child collection by condition

    • Description: This query is commonly used when you have a parent-child relationship and want to filter the child collection based on a certain condition.
    var filteredParents = parents.Where(p => p.Children.Any(c => c.Condition));

  2. LINQ filter child collection by property value

    • Description: This query filters parent entities based on a specific property value in their child collection.
    var filteredParents = parents.Where(p => p.Children.Any(c => c.Property == value));

  3. LINQ filter child collection with multiple conditions

    • Description: Useful when you need to filter parent entities based on multiple conditions within their child collections.
    var filteredParents = parents.Where(p => p.Children.Any(c => c.Condition1 && c.Condition2));

  4. LINQ filter child collection and return parent entities

    • Description: This query filters child entities based on certain conditions and returns their parent entities.
    var filteredParents = parents.Where(p => p.Children.Any(c => c.Condition)).ToList();

  5. LINQ filter child collection by child entity property

    • Description: Filters parent entities based on the property value of their child entities.
    var filteredParents = parents.Where(p => p.Children.Any(c => c.Property == value));

  6. LINQ filter child collection by child entity property with ordering

    • Description: Filters parent entities based on a property value of their child entities and orders the result.
    var filteredParents = parents.Where(p => p.Children.Any(c => c.Property == value)) .OrderBy(p => p.Property);

  7. LINQ filter child collection by child entity property and count

    • Description: Filters parent entities based on a property value of their child entities and ensures a certain count.
    var filteredParents = parents.Where(p => p.Children.Count(c => c.Property == value) > count);

  8. LINQ filter child collection by child entity property and sum of another property

    • Description: Filters parent entities based on a property value of their child entities and the sum of another property.
    var filteredParents = parents.Where(p => p.Children.Sum(c => c.Property1) > value && p.Children.Any(c => c.Property2 == value2));

  9. LINQ filter child collection by child entity property and distinct parent entities

    • Description: Filters parent entities based on a property value of their child entities and ensures distinct parent entities.
    var filteredParents = parents.Where(p => p.Children.Any(c => c.Property == value)).Distinct();

  10. LINQ filter child collection by multiple child entity properties

    • Description: Filters parent entities based on multiple properties of their child entities.
    var filteredParents = parents.Where(p => p.Children.Any(c => c.Property1 == value1 && c.Property2 == value2));

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