using System;

using System.Linq;

using System.Xml.Linq;

​

public class Program

{

    public static void Main()

    {

        const string xml =

            @"<Report xmlns:rd=""http://schemas.microsoft.com/SQLServer/reporting/reportdesigner"" xmlns:cl=""http://schemas.microsoft.com/sqlserver/reporting/2010/01/componentdefinition"" xmlns=""http://schemas.microsoft.com/sqlserver/reporting/2010/01/reportdefinition"">

  <Author>© Piet</Author>

  <AutoRefresh>0</AutoRefresh>

  <DataSources>

    <DataSource Name=""DW_Tables"">

      <DataSourceReference>DW_Tables</DataSourceReference>

      <rd:SecurityType>None</rd:SecurityType>

      <rd:DataSourceID>84cf022a-c58e-4286-8bc8-bca2c0358206</rd:DataSourceID>

    </DataSource>

  </DataSources>

</Report>";

​

        var doc = XDocument.Parse(xml);

​

        XNamespace ns = "http://schemas.microsoft.com/sqlserver/reporting/2010/01/reportdefinition";

        var sources = doc.Descendants(ns + "DataSources");

​

        Console.WriteLine(sources.Count());

    }

}

​