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Specification Pattern
Specification Design Pattern is created to ensure that the logical rules in an object are received from the outside. The rules of business are in a chain of successive chains, which may also reveal a more complex business rule.
I want to continue with a code example to understand the pattern. In repository Specification Pattern implemented by interface definition ;
public interface ISpecification<T> { Expression<Func<T, bool>> Criteria { get; } List<Expression<Func<T, object>>> Includes { get; } List<string> IncludeStrings { get; } Expression<Func<T, object>> OrderBy { get; } Expression<Func<T, object>> OrderByDescending { get; } int Take { get; } int Skip { get; } bool isPagingEnabled { get; } }These definition and below implementation located in Core layer. Because these classes not included Entity Framework Core related dependencies.
public abstract class BaseSpecification<T> : ISpecification<T> { protected BaseSpecification(Expression<Func<T, bool>> criteria) { Criteria = criteria; } public Expression<Func<T, bool>> Criteria { get; } public List<Expression<Func<T, object>>> Includes { get; } = new List<Expression<Func<T, object>>>(); public List<string> IncludeStrings { get; } = new List<string>(); public Expression<Func<T, object>> OrderBy { get; private set; } public Expression<Func<T, object>> OrderByDescending { get; private set; } public int Take { get; private set; } public int Skip { get; private set; } public bool isPagingEnabled { get; private set; } = false; protected virtual void AddInclude(Expression<Func<T, object>> includeExpression) { Includes.Add(includeExpression); } protected virtual void AddInclude(string includeString) { IncludeStrings.Add(includeString); } protected virtual void ApplyPaging(int skip, int take) { Skip = skip; Take = take; isPagingEnabled = true; } protected virtual void ApplyOrderBy(Expression<Func<T, object>> orderByExpression) { OrderBy = orderByExpression; } protected virtual void ApplyOrderByDescending(Expression<Func<T, object>> orderByDescendingExpression) { OrderByDescending = orderByDescendingExpression; } }Specification Pattern implemented from Microsoft article.
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