Karmencita: an object query language for .NET

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Introduction

Karmencita is an object query language for .NET. Its purpose is to allow easy querying from in-memory structured data.

Features:

• an easy, SQL-like language.
• common, slim API used for querying data.
• supports any IEnumerable data source, DataTables and XmlDataDocuments.
• extensible implementation.
• common API, but still gets results depending on the data source. (For instance, when querying XmlDataDocuments, we get back a XmlElement[]. But if we query a DataTable, we get back a DataRow[]).
• supports IComparable for custom type implementation.

The basic idea is to have an easy SQL-like language in which we can write queries against any data source.

Using the code

Let's see some code samples:

• query the list of running processes:

  // get an array of running processes
  Process[] proc = Process.GetProceses();
  
  // initialize Karmencita with
  // the type of object to be queries
  ObjectQuery<Process> oq = 
          new ObjectQuery<Process>();
  
  // write the query
  string query = "BasePriority > 3 and Responding" + 
                 " = true and MainWindowTitle Like C%";
  
  //run the query
  Process[] processes = (Process[]) oq.Select(proc, query);

• query a Stack<> of Customer objects:

  // initialize the data source
  // (in this case a Stack of Customers)
  Stack<Customer> proc = .....
  
  // initialize Karmencita with
  // the type of object to be queries
  ObjectQuery<Customer> oq = 
            new ObjectQuery<Customer>();
  
  // write the query
  string query = "Name = [Thor the Mighty]" + 
                 " and IsMale = true and BirthDate" + 
                 " < [1,1,1910]";
  
  //run the query
  Customer[] processes = (Customer[]) oq.Select(proc, query);

• query a DataTable:

  // load the DataTable from the database
  DataTable dt = .....
  
  // initialize Karmencita with
  // the type of object to be queries
  ObjectQuery<DataTable> oq = 
           new ObjectQuery<DataTable>();
  
  // write the query
  string query = "ProductName = Fish and" + 
                 " UnitPrice > 200 and IsInStock = true";
  
  //run the query
  DataRow[] processes = (DataRow[]) oq.Select(proc, query);

• query an XMLDataDocument:

  // load the XML document
  DataTable dt = .....
  
  // initialize Karmencita with the type
  // of object to be queries
  ObjectQuery<XMLDataDocument> oq = 
      new ObjectQuery<XMLDataDocument>();
  
  // write the query
  string query = "ProductName = Fish and" + 
                 " UnitPrice > 200 and IsInStock = true";
  
  //run the query
  XmlElement[] processes = (XmlElement[]) oq.Select(proc, query);

Conclusion

As you can see, Karmencita is a generic query engine which can be used to query multiple data sources. Just throw a data source and a query to it, and have the result. No need to muck around with multiple query syntaxes (DataTable .Select, XQuery etc.). One generic query language to rule them all. :)

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