Kkts.Expressions
Build string expression to lambda expression to support dynamic query from UI
get via nuget Kkts.Expressions
Sample class
class Data
{
public int Id { get; set; }
public string Name { get; set; }
public bool IsEnabled { get; set; }
public DateTime CreationDate { get; set; }
// ...
}
public class TestDbContext : DbContext
{
// ...
public DbSet<Data> Entities { get; set; }
// ...
}Usage 1
// The property name is case insensitive for example id and Id are the same
EvaluationResult<Data, bool> evaluationResult = Interpreter.ParsePredicate<Data>("id = 1 and name='Test'");
// Use EvaluationResult to get validation result
// Should check if evaluationResult.Succeeded
Expression<Func<Data, bool>> predicate = evaluationResult.Result;
// Equivalent
var filters = new Filter[]
{
new Filter{ Property = "id", Operator = "=", Value = "1" },
// and
new Filter{ Property = "name", Operator = "=", Value = "Test" }
};
Expression<Func<Data, bool>> predicate = filters.BuildPredicate<Data>();
// Or use filters.TryBuildPredicate<Data>() to get validation resultUsage 2
// The property name is case insensitive for example id and Id are the same
Expression<Func<Data, bool>> predicate = Interpreter.ParsePredicate<Data>("(id = 1 and name='Test1') or (id = 2 and name='Test2')").Result;
// Equivalent
var filters = new FilterGroup[]
{
new FilterGroup
{
Filters = new List<Filter>
{
new Filter{ Property = "id", Operator = "=", Value = "1" },
// and
new Filter{ Property = "name", Operator = "=", Value = "Test1" }
}
},
// or
new FilterGroup
{
Filters = new List<Filter>
{
new Filter{ Property = "id", Operator = "=", Value = "2" },
// and
new Filter{ Property = "name", Operator = "=", Value = "Test2" }
}
}
}
Expression<Func<Data, bool>> predicate = filters.BuildPredicate<Data>();
// Or use filters.TryBuildPredicate<Data>() to get validation resultUsage 3 (Order By)
// The property name is case insensitive for example id and Id are the same
var context = new TestDbContext();
// Order by Id then by Name descending (the direction is empty or asc or desc, the empty is the same asc)
var ordered = context.Entities.OrderBy("Id, Name desc");
// Equivalent
var ordered = context.Entities.OrderBy(new[]
{
{ new OrderByInfo { Property = "Id" },
{ new OrderByInfo { Property = "Name", Descending = true }
}
// or
var evaluationResult = context.Entities.TryOrderBy(...);
if (evaluationResult.Succeeded) var ordered = evaluationResult.Result;Usage 4 (Variables) - V2 introduces Query Variables Examples
// It has 2 default variables: now, utcnow (they are case insensitive)
Expression<Func<Data, bool>> predicate = Interpreter.ParsePredicate<Data>("CreationDate = now or CreationDate = utcnow").Result;
// Equivalent in c#
Expression<Func<Data, bool>> predicate = p => p.CreationDate == DateTime.Now || p.CreationDate == DateTime.UtcNow;
// We can compare the year, month, day, ... like
Expression<Func<Data, bool>> predicate = Interpreter.ParsePredicate<Data>("CreationDate.year = now.year").Result;
// From V2 It is applied Query Variables by adding prefix $ before a variable
Expression<Func<Data, bool>> predicate = Interpreter.ParsePredicate<Data>("CreationDate.year = $now.year").Result;Usage 5 (Custom Variables) - V2 introduces 2 new ways to declare variables Examples
V2 introduces ParsePredicateAsync
class UserInfo
{
public string UserName { get; set; }
public int Id { get; set; }
}
class CustomVariableResolver : VariableResolver
{
public UserInfo User { get; } = new UserInfo { Id = 1, UserName = "linhle" };
}
// Now it has new variables user.id and user.username
Expression<Func<Data, bool>> predicate = Interpreter.ParsePredicate<Data>("name = user.username and id = user.id", variableResolver: new CustomVariableResolver()).Result;
// V2 introduces Async
EvaluationResult<T, bool> result = await Interpreter.ParsePredicateAsync<Data>("name = user.username and id = user.id", variableResolver: new CustomVariableResolver()); Usage 5 (Valid Properties)
// Only accept Id in predicate, if other properties occurs in predicate, an exception will be thrown
Expression<Func<Data, bool>> predicate = Interpreter.ParsePredicate<Data>("id = 1 and name='Test'", validProperties: new[] { "Id" }).Result; // throw an exceptionUsage 6 (Condition)
// The options can be deserialized from JSON
var options = new ConditionOptions
{
OrderBy = "...",
OrderBys = new[] { new OrderByInfo { ... } },
Filters = new[] { new Filter { ... } },
FilterGroups = new[] { new FilterGroup { Filters = new[] { ... } } },
Where = "..."
}
var condition = options.BuildCondition<Data>();
var context = new TestDbContext();
// Should check if condition.IsValid before calling where
var result = context.Entities.Where(condition).ToList();
// or paging
var result = context.Entities.Take(condition, new Pagination { Offset = 10, Limit = 10 });
var result = context.Entities.Take(condition, new Pagination { Page = 2, PageSize = 10 });
// or paging with total records count
var result = context.Entities.TakePage(condition, new Pagination { Offset = 10, Limit = 10 });
var result = context.Entities.TakePage(condition, new Pagination { Page = 2, PageSize = 10 });Usage 7 (Property Mapping)
// map entityId as Id
var mapping = new Dictionary<string, string>
{
["entityId"] = "Id"
};
Expression<Func<Data, bool>> predicate = Interpreter.ParsePredicate<Data>("(entityId = 1 and name='Test1') or (entityId = 2 and name='Test2')", propertyMapping: mapping).Result;
// Equivalent
var filters = new FilterGroup[]
{
new FilterGroup
{
Filters = new List<Filter>
{
new Filter{ Property = "entityId", Operator = "=", Value = "1" },
// and
new Filter{ Property = "name", Operator = "=", Value = "Test1" }
}
},
// or
new FilterGroup
{
Filters = new List<Filter>
{
new Filter{ Property = "entityId", Operator = "=", Value = "2" },
// and
new Filter{ Property = "name", Operator = "=", Value = "Test2" }
}
}
}
Expression<Func<Data, bool>> predicate = filters.BuildPredicate<Data>(propertyMapping: mapping);Usage 8 (Applies to V2 - Query Variables in In Operator) Examples
Support operators
| Operator | Usage | Support data types |
|---|---|---|
| Equals | Id = 1 or Id == 1 | Number, String, Guid, Boolean, DateTime, DateTimeOffset, Enum, Nullable |
| Not Equals | Id != 1 or Id <> 1 | Number, String, Guid, Boolean, DateTime, DateTimeOffset, Enum, Nullable |
| Less than | Id < 1 | Number, DateTime, DateTimeOffset, Nullable |
| Less than or Equal | Id <= 1 | Number, DateTime, DateTimeOffset, Nullable |
| Greater than | Id > 1 | Number, DateTime, DateTimeOffset, Nullable |
| Greater than or Equal | Id >= 1 | Number, DateTime, DateTimeOffset, Nullable |
| In | Id in [1, 2, 3, 4] or Name in ['String1', 'String2'] | Number, String, Guid, DateTime, DateTimeOffset, Enum, Nullable |
| Contains | Name.contains('Text') or Name @ 'Text' | String |
| Starts with | Name.startsWith('Text') or Name @* 'Text' | String |
| Ends with | Name.endsWith('Text') or Name *@ 'Text' | String |
| Not | !IsEnabled or not(IsEnabled) or not(Id = 1) or !(Id = 1) | Boolean |
| Logical and (and or &&) | Id = 1 and Name = "Text" | Boolean |
| Logical or (or or ||) | Id = 1 or Name = "Text" | Boolean |
Contacts
LinkedIn Skype: linh.nhat.le