amnats / qbt-net

Query by Text in C#

Query by Text in C#

In a yak shaving accident I implemented a stripped down version of the OData provider. One can even say that it was a good exercise in understanding C# expression trees and LINQ queries. All that this library can do is transform a text query into an expression tree consumable by a LINQ provider.

It can recognise field names and even discern strings from numbers!

Example

var expressionBuilder { get; } = new FilterExpressionBuilder<User>();

var filterStr = "userName eq 'Luke Skywalker'";
var expr = expressionBuilder.TranslateToExpression(filterStr);
var filtered = Users.Where(expr).ToList();

Assert.That(filtered.Count, Is.EqualTo(1));
Assert.That(filtered.First.UserName, Is.EqualTo("Luke Skywalker"));

public class User
{
  public string UserName { get; set; }
}

Supported binary operators:

• eq Equal
• ne Not equal
• gt Greater than
• lt Less than
• ge Grater than or equal
• le Less than or equal
• and And
• or Or

Nice things to have in future:

• Support both for camel case and pascal case field names in the text query
• Support for more than one operator at a time
• Bracket support
• Order by
• First
• Last
• string methods e.g. contains, endswith etc.
• Take
• Offset
• Escaping characters