WPF : Dynamic Search Driven List Results

At work at the moment I am working on a way way cool customisable search that basically allows user to pick source entities and related entities and then pick what fields they would like to show, this is similar to Microsoft’s CRM Dynamics product, which allows very very sophisticated searches to be produces, by the use of a nice search UI.

Here is what CRM looks like. The search we actually built at work is even better than this, but for NDA reasons I can not show.

From our search we create a strongly typed Query object, which is sent across a WCF service boundary and when received at the other end, in converted to dynamic SQL, and is the run against a SQL database. Yes that right we created our own LINQ effectively. Its call GNRSQL.

Anyway as a side effect from being able to search for anything from anywhere, we also needed the ability for our search results grid to dynamically adjust to any results set. To compound this our results objects are hierarchical in nature, and we are using the Infragistics XamDataGrid, which wants to show things in a hierarchical manner. Which is not what we wanted, so we needed to flatten the results from a hierarchy to a flat structure.

Your 1st thought might be, oh just send a DataTable across the WCF boundary, this is not a good idea, the serialization of DataTable(s) and WCF is very strange, and also incredibly heavy. Basically the namespaces get messed up and so do some of the internal field names, and my god the serialization is so far from pretty.

So we had to try some other things.

My next idea was to use IEnumerable and use LINQ to pluck out only those properties that we wanted to show based on the actually results obtained. Our results contained metadata that we could use to construct a LINQ query which would return a flattened IEnumerable of anonymous types, that had only the properties we wanted. Choosing of properties was driven by examining the actual results metadata. And all this has to happen at runtime. Doing this at design time is dead simple we can just do something like (assuming we have a list of results already)

var newFlattenedResults = (from x in results select new { ID = x.IDField, DateOfOrder=x.OrderDate });

But how could you create something that could be used in this manner, and tailored to suit the properties returned by the search, but done at runtime. The rest of this post will show you how.

Dynamic Assemblies

.NET comes equipped with the ability to produce dynamic assemblies on the fly at runtime. So lets start there and have a look at a helper class for making this process easy.

  1:  using System.Reflection;
  2:  using System.CodeDom.Compiler;
  3:  using Microsoft.CSharp;
  4:
  5:  using System;
  6:  using System.Collections.Generic;
  7:  using System.Text;
  8:
  9:  namespace DynamicLINQ
 10:  {
 11:      /// <summary>
 12:      /// Utlilty class. Compliles and runs assemblies
 13:      /// on the fly, with the option to invoke a method
 14:      /// and return the results from the chosen
 15:      /// method
 16:      /// </summary>
 17:      public class DynamicCompiler
 18:      {
 19:          #region Public Methods
 20:          /// <summary>
 21:          /// Compiles the code and either returns the compiled code as a Type
 22:          /// or creates compiled code as a Type, and invokes the created Types
 23:          /// method. Where the method is picked by the user
 24:          /// </summary>
 25:          /// <typeparam name="T">Type of T to use</typeparam>
 26:          /// <param name="code">code to compile</param>
 27:          /// <param name="nameSpace">namespace to use for compiled code</param>
 28:          /// <param name="classToLoad">class name</param>
 29:          /// <param name="methodToRun">method to invoke (optional)</param>
 30:          /// <param name="ShouldImvokeMethod">true if you want to
 31:          /// invoke the method</param>
 32:          /// <returns>Type of T to use</returns>
 33:          public T ComplileAndRun<T>(String code, String nameSpace,
 34:              String classToLoad, string methodToRun, Boolean ShouldImvokeMethod)
 35:          {
 36:              try
 37:              {
 38:                  String lcCode = code;
 39:
 40:                  var provider = new CSharpCodeProvider(
 41:                          new Dictionary<String, String>()
 42:                              { { "CompilerVersion", "v3.5″ } });
 43:
 44:                  CompilerParameters parameters = new CompilerParameters();
 45:
 46:                  // Start by adding any referenced assemblies
 47:                  parameters.ReferencedAssemblies.Add("System.dll");
 48:                  parameters.ReferencedAssemblies.Add(
 49:                      typeof(Demo.Data.Person).Assembly.Location);
 50:                  parameters.ReferencedAssemblies.Add(
 51:                      typeof(System.Linq.Enumerable).Assembly.Location);
 52:
 53:
 54:                  // Load the resulting assembly into memory
 55:                  parameters.GenerateInMemory = true;
 56:                  // Now compile the whole thing
 57:                  //Must create a fully functional assembly as the code string
 58:                  CompilerResults compiledCode =
 59:                      provider.CompileAssemblyFromSource(parameters, lcCode);
 60:
 61:                  if (compiledCode.Errors.HasErrors)
 62:                  {
 63:                      String errorMsg = String.Empty;
 64:                      errorMsg = compiledCode.Errors.Count.ToString() +
 65:                                 " n Dynamically generated code threw an error. n Errors:";
 66:
 67:                      for (int x = 0; x < compiledCode.Errors.Count; x++)
 68:                      {
 69:                          errorMsg = errorMsg + "rnLine: " +
 70:                                     compiledCode.Errors[x].Line.ToString() + " - " +
 71:                                     compiledCode.Errors[x].ErrorText;
 72:                      }
 73:
 74:                      throw new Exception(errorMsg);
 75:                  }
 76:
 77:                  Assembly assembly = compiledCode.CompiledAssembly;
 78:
 79:                  // Retrieve an obj ref â€" generic type only
 80:                  object instance = assembly.CreateInstance(
 81:                      nameSpace + "." + classToLoad);
 82:
 83:                  //invoke the method if needs be, and get results
 84:                  //back from method invocation
 85:                  if (ShouldImvokeMethod)
 86:                  {
 87:                      if (instance == null)
 88:                          return default(T);
 89:
 90:                      T result = (T)instance.GetType().InvokeMember(
 91:                             methodToRun, BindingFlags.InvokeMethod,
 92:                             null, instance, new object[0]);
 93:
 94:                      return result;
 95:                  }
 96:                  else
 97:                  {
 98:                      return (T)instance;
 99:                  }
100:              }
101:              catch (Exception ex)
102:              {
103:                  Console.WriteLine(String.Format(
104:                      "An exception occurred {0}", ex.Message));
105:                  return default(T);
106:              }
107:          }
108:          #endregion
109:      }
110:  }

So using this helper class we can construct an in memory assembly and call a method within an object within it, or simply return the newly created object within the dynamic assembly.

So lets continue our journey, and look at a small XAML app, where there is a ListView that starts with the following columns

Where the XAML for this screen looks like this

 1:  <Window x:Class="DynamicLINQ.Window1″
 2:      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 3:      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 4:          WindowStartupLocation="CenterScreen"
 5:      Title="Window1″ Height="300″ Width="700″>
 6:      <DockPanel LastChildFill="True">
 7:          <StackPanel DockPanel.Dock="Top" Orientation="Horizontal"
 8:                      HorizontalAlignment="Stretch" Background="CornflowerBlue">
 9:              <Button x:Name="ShowAll" Content="Show All" Margin="5″
10:                      Click="ShowAll_Click"/>
11:              <Button x:Name="ShowSome" Content="Show Some Columns" Margin="5″
12:                      Click="ShowSome_Click"/>
13:          </StackPanel>
14:
15:
16:          <ListView x:Name="lvItems" >
17:              <ListView.View>
18:                  <GridView>
19:                      <GridViewColumn Header="Age"
20:                                      DisplayMemberBinding="{Binding Age}" />
21:                      <GridViewColumn Header="FirstName"
22:                                      DisplayMemberBinding="{Binding FirstName}" />
23:                      <GridViewColumn Header="MiddleName"
24:                                      DisplayMemberBinding="{Binding MiddleName}" />
25:                      <GridViewColumn Header="LastName"
26:                                      DisplayMemberBinding="{Binding LastName}" />
27:                      <GridViewColumn Header="LastName"
28:                                      DisplayMemberBinding="{Binding LastName}" />
29:                      <GridViewColumn Header="ID"
30:                                      DisplayMemberBinding="{Binding ID}" Width="230″ />
31:                      <GridViewColumn Header="DOB"
32:                                      DisplayMemberBinding="{Binding Dob}" Width="130″ />
33:                  </GridView>
34:              </ListView.View>
35:          </ListView>
36:
37:
38:      </DockPanel>
39:  </Window>

You can see that the initial columns for the displayed results are static at this point, and are showing the results of being bound to a List<Person> objects, where a Person looks like this

  1:  using System;
  2:  using System.Collections.Generic;
  3:  using System.Linq;
  4:  using System.Text;
  5:  using System.ComponentModel;
  6:
  7:  namespace Demo.Data
  8:  {
  9:      public class Person : INotifyPropertyChanged
 10:      {
 11:          #region Data
 12:          public Int32 age;
 13:          public String firstName;
 14:          public String middleName;
 15:          public String lastName;
 16:          public AdditionalData personData;
 17:          #endregion
 18:
 19:          #region Public Properties
 20:          public Int32 Age
 21:          {
 22:              get { return age; }
 23:              set
 24:              {
 25:                  age = value;
 26:                  NotifyPropertyChanged("Age");
 27:              }
 28:          }
 29:
 30:          public String FirstName
 31:          {
 32:              get { return firstName; }
 33:              set
 34:              {
 35:                  firstName = value;
 36:                  NotifyPropertyChanged("FirstName");
 37:              }
 38:          }
 39:
 40:          public String MiddleName
 41:          {
 42:              get { return middleName; }
 43:              set
 44:              {
 45:                  middleName = value;
 46:                  NotifyPropertyChanged("MiddleName");
 47:              }
 48:          }
 49:
 50:          public String LastName
 51:          {
 52:              get { return lastName; }
 53:              set
 54:              {
 55:                  lastName = value;
 56:                  NotifyPropertyChanged("LastName");
 57:              }
 58:          }
 59:
 60:          public AdditionalData PersonData
 61:          {
 62:              get { return personData; }
 63:              set
 64:              {
 65:                  personData = value;
 66:                  NotifyPropertyChanged("PersonData");
 67:              }
 68:          }
 69:          #endregion
 70:
 71:          #region INotifyPropertyChanged region
 72:          public event PropertyChangedEventHandler PropertyChanged;
 73:
 74:          private void NotifyPropertyChanged(String info)
 75:          {
 76:              if (PropertyChanged != null)
 77:              {
 78:                  PropertyChanged(this, new PropertyChangedEventArgs(info));
 79:              }
 80:          }
 81:          #endregion
 82:      }
 83:
 84:      public class AdditionalData : INotifyPropertyChanged
 85:      {
 86:          #region Data
 87:          private Guid id;
 88:          private DateTime dob;
 89:          #endregion
 90:
 91:          #region Public Properties
 92:          public Guid ID
 93:          {
 94:              get { return id; }
 95:              set
 96:              {
 97:                  id = value;
 98:                  NotifyPropertyChanged("Id");
 99:              }
100:          }
101:
102:          public DateTime Dob
103:          {
104:              get { return dob; }
105:              set
106:              {
107:                  dob = value;
108:                  NotifyPropertyChanged("Dob");
109:              }
110:          }
111:          #endregion
112:
113:          #region INotifyPropertyChanged region
114:          public event PropertyChangedEventHandler PropertyChanged;
115:
116:          private void NotifyPropertyChanged(String info)
117:          {
118:              if (PropertyChanged != null)
119:              {
120:                  PropertyChanged(this, new PropertyChangedEventArgs(info));
121:              }
122:          }
123:          #endregion
124:      }
125:
126:  }

So now let us see what would happen if we simulated some other search results coming back, from somewhere else, that should alter what is shown in the search results ListView.

 1:  private void ShowSome_Click(object sender, RoutedEventArgs e)
 2:  {
 3:      //show some columns from Dynamically compiled LINQ
 4:      //query
 5:      IEnumerable results =
 6:          enumerableResultsCreator.ObtainFlattenedResults(lvItems,
 7:              people, WritePropertyType.Some);
 8:
 9:
10:      lvItems.ItemsSource = results;
11:
12:  }

Where people is simply a list of Person objects set up with some Person objects in it (obviously I am faking the search results part, for the sake of this article, the Person objects, would actually be some search results or something coming from the results of a search, but for this example it doesn’t matter, as I am just trying to show you how to dynamically work with LINQ at runtime)

1:  private List<Person> people = new List<Person>();

You can see from the above code that we use a method called ObtainFlattenedResults() which is available in the following helper class

  1:  using System;
  2:  using System.Collections;
  3:  using System.Collections.Generic;
  4:  using System.Linq;
  5:  using System.Reflection;
  6:  using System.Text;
  7:
  8:  using Demo.Data;
  9:  using System.Windows.Controls;
 10:  using System.Windows.Data;
 11:
 12:
 13:  namespace DynamicLINQ
 14:  {
 15:
 16:      public enum WritePropertyType { All = 1, Some };
 17:
 18:      public class EnumerableResultsCreator
 19:      {
 20:          #region Data
 21:          private readonly String generatedNamespace = "DynamicLINQ";
 22:          private readonly String generatedClassName = "ResultsWriter";
 23:          private readonly String generatedMethod = "GetResults";
 24:          private List<Person> originalResults = null;
 25:          private WritePropertyType currentPropertyType =
 26:              WritePropertyType.All;
 27:          #endregion
 28:
 29:          #region Ctor
 30:          public EnumerableResultsCreator()
 31:          {
 32:
 33:          }
 34:          #endregion
 35:
 36:          #region Private Methods
 37:
 38:          /// <summary>
 39:          /// Writes out code for class to dynamically compile
 40:          /// </summary>
 41:          private String WriteDynamicClass(WritePropertyType currentPropertyType)
 42:          {
 43:              StringBuilder code = new StringBuilder();
 44:              code.AppendLine(" using System; ");
 45:              code.AppendLine(" using System.Collections.Generic;");
 46:              code.AppendLine(" using System.Collections.ObjectModel;");
 47:              code.AppendLine(" using System.Linq;");
 48:              code.AppendLine(" using System.Text;");
 49:              //Where the DataLayer objects live
 50:              code.AppendLine(" using Demo.Data; ");
 51:              code.AppendFormat(" namespace {0}", generatedNamespace);
 52:              code.AppendLine();
 53:              code.AppendLine(" {");
 54:              code.AppendFormat(" public class {0}", generatedClassName);
 55:              code.AppendLine();
 56:              code.AppendLine(" {");
 57:              code.AppendFormat("{0}",
 58:                  this.WriteCodeProperties(currentPropertyType));
 59:              code.AppendLine();
 60:              code.Append(" }");
 61:              code.AppendLine();
 62:              code.Append(" }");
 63:              code.AppendLine();
 64:              return code.ToString();
 65:          }
 66:
 67:
 68:          /// <summary>
 69:          /// Either writes a LINQ query string that returns an anomomous
 70:          /// set of object with ALL properties, or just some of the properties
 71:          /// </summary>
 72:          private String WriteCodeProperties(WritePropertyType currentPropertyType)
 73:          {
 74:              StringBuilder builder = new StringBuilder();
 75:              builder.AppendFormat(
 76:                  "n public Object {0}(List<Person> results)",
 77:                      generatedMethod);
 78:              builder.AppendLine("{");
 79:
 80:
 81:              switch (currentPropertyType)
 82:              {
 83:                  case WritePropertyType.All:
 84:                      //OK this is a static query that could have been done in  standard LINQ
 85:                      //but this techniqe can be used to create dyanamically created
 86:                      //LINQ queries at runtime
 87:                      builder.AppendLine("var x =(from r in results select new { ");
 88:                      builder.AppendLine("         Age = r.Age,FirstName = r.FirstName,");
 89:                      builder.AppendLine("         MiddleName=r.MiddleName, LastName = r.LastName,");
 90:                      builder.AppendLine("         ID = r.PersonData.ID, Dob = r.PersonData.Dob });");
 91:                      builder.AppendLine("return x;");
 92:                      builder.AppendLine("}");
 93:                      break;
 94:                  case WritePropertyType.Some:
 95:                      //OK this is a static query that could have been done in  standard LINQ
 96:                      //but this techniqe can be used to create dyanamically created
 97:                      //LINQ queries at runtime
 98:                      builder.AppendLine("var x =(from r in results select new { ");
 99:                      builder.AppendLine("         Age = r.Age,FirstName = r.FirstName,");
100:                      builder.AppendLine("         LastName = r.LastName});");
101:                      builder.AppendLine("return x;");
102:                      builder.AppendLine("}");
103:                      break;
104:              }
105:
106:
107:              return builder.ToString();
108:
109:          }
110:
111:          /// <summary>
112:          /// Creates the new columns for the Dynamically retrieved
113:          /// results
114:          /// </summary>
115:          private void CreateListViewColumns(IEnumerable result, ListView lv)
116:          {
117:              GridView gv = new GridView();
118:
119:              IEnumerator e = result.GetEnumerator();
120:              while (e.MoveNext())
121:              {
122:                  Type t = e.Current.GetType();
123:                  PropertyInfo[] infos = t.GetProperties();
124:
125:                  foreach (var item in infos)
126:                  {
127:                      GridViewColumn column = new GridViewColumn();
128:                      column.Header = item.Name;
129:                      Binding binding = new Binding(item.Name);
130:
131:                      column.DisplayMemberBinding = binding;
132:                      gv.Columns.Add(column);
133:                  }
134:                  break;
135:              }
136:
137:              lv.View = gv;
138:          }
139:
140:
141:          #endregion
142:
143:          #region Public Method
144:          /// <summary>
145:          /// Create the dynamic Type invoke its method
146:          /// and get the results
147:          /// </summary>
148:          public IEnumerable ObtainFlattenedResults(
149:              ListView lv,
150:              List<Person> originalResults,
151:              WritePropertyType currentPropertyType)
152:          {
153:              if (originalResults.Count == 0)
154:                  return null;
155:
156:              this.originalResults = originalResults;
157:
158:              //Create the DynamicCompiler
159:              DynamicCompiler compiler = new DynamicCompiler();
160:
161:              //Get the newly compiled object
162:              Object dynaClass = compiler.ComplileAndRun<Object>(
163:                  this.WriteDynamicClass(currentPropertyType),
164:                  generatedNamespace, generatedClassName, "", false);
165:
166:              //invoke its method to get the result
167:              IEnumerable result =
168:                  (IEnumerable)dynaClass.GetType().InvokeMember(
169:                          generatedMethod, BindingFlags.InvokeMethod,
170:                          null, dynaClass, new object[1]
171:                              { this.originalResults });
172:
173:              //create new ListView columns
174:              CreateListViewColumns(result, lv);
175:
176:
177:              return result;
178:
179:          }
180:          #endregion
181:
182:      }
183:  }

So what this class does, is construct a new code file, that is compiled using the DynamicCompiler helper class that I showed you earlier. What we then do is get an actual instance of an object back from the dynamic compilation process, which we can then use to invoke a method on.

Here is what the compiled code will look like

 1:  using System;
 2:  using System.Collections.Generic;
 3:  using System.Collections.ObjectModel;
 4:  using System.Linq;
 5:  using System.Text;
 6:  using Demo.Data;
 7:  namespace DynamicLINQ
 8:  {
 9:      public class ResultsWriter
10:      {
11:
12:          public Object GetResults(List<Person> results)
13:          {
14:              var x = (from r in results
15:                       select new
16:                       {
17:                           Age = r.Age,
18:                           FirstName = r.FirstName,
19:                           LastName = r.LastName
20:                       });
21:              return x;
22:          }
23:
24:      }
25:  }

So you can see that we are creating an actual class that accepts a List<Person> (the fake search results) and uses some LINQ to grab out ONLY the properties we want to use all rolled up in an anonymous which is selected as a single flattened search result for the search results grid. Remember this is all happening at RUNTIME, so we can do what we like, we can manipulate the results as much as we like, as the code we compile is just a String.

The other thing that happens is that the WPF ListView columns are altered to only show the necessary columns based on the newly flattened search results.

Some grid works nicer with anonymous types, though so far the WPF Toolkit DataGrid failed, and so does the ListView, that is why we need to do the trick with re-creating the columns based on the new results. At work we are using the Infragistics xamDataGrid, and it works straight out of the can with anonymous types, we do not have to mess about with columns at all, it just knows what to do.

Here is the results

Showing ALL Columns Of Results

Which is done using the following logic

 1:                  case WritePropertyType.All:
 2:                      //OK this is a static query that could have been done in  standard LINQ
 3:                      //but this techniqe can be used to create dyanamically created
 4:                      //LINQ queries at runtime
 5:                      builder.AppendLine("var x =(from r in results select new { ");
 6:                      builder.AppendLine("         Age = r.Age,FirstName = r.FirstName,");
 7:                      builder.AppendLine("         MiddleName=r.MiddleName, LastName = r.LastName,");
 8:                      builder.AppendLine("         ID = r.PersonData.ID, Dob = r.PersonData.Dob });");
 9:                      builder.AppendLine("return x;");
10:                      builder.AppendLine("}");

Showing Selected Columns Of Results (see we only get some of the columns)

Which is done using the following logic

 1:                  case WritePropertyType.Some:
 2:                      //OK this is a static query that could have been done in  standard LINQ
 3:                      //but this techniqe can be used to create dyanamically created
 4:                      //LINQ queries at runtime
 5:                      builder.AppendLine("var x =(from r in results select new { ");
 6:                      builder.AppendLine("         Age = r.Age,FirstName = r.FirstName,");
 7:                      builder.AppendLine("         LastName = r.LastName});");
 8:                      builder.AppendLine("return x;");
 9:                      builder.AppendLine("}");
10:                      break;

Here is a small demo project

http://sachabarber.net/wp-content/uploads/2009/04/dynamiclinq.zip

Now I know this is a very specific business case, and not many people will do this