In Composite C1, developers can define KeySelector values in a data type via C# code. This can be useful if it is necessary to define values for a  data form's dropdowns.

Let’s consider the following example and see how it can be done.

1. Add this code as .cs file in the /App_Code folder:
   

   using System.Collections.Generic;
   
   namespace Examples.DataForms
   {
       public class DropDownStrings
       {
           public static IEnumerable<string> GetStrings()
           {
               List<string> list = new List<string>();
               list.Add("String 1");
               list.Add("String 2");
               list.Add("String 3");
               return list;
           }
   
           public static IEnumerable<string> GetStringsWithParameters(bool IsTrue)
           {
               List<string> list = new List<string>();
               if (IsTrue)
                   list.Add("Parameter = TRUE");
               else
                   list.Add("Parameter = FALSE");
               return list;
           }
   
           public static Dictionary<string, string> GetStringsAsKeyValuePairs()
           {
               Dictionary<string, string> keysValues = new Dictionary<string, string>();
               keysValues.Add("Key 1", "Value 1");
               keysValues.Add("Key 2", "Value 2");
               keysValues.Add("Key 3", "Value 3");
               return keysValues;
           }
       }
   }

   
   Download the source
   
2. Create a global data type that contains 3 string fields: "SimpleString", "ParametrizedString" and "KeyValueString".
3. Edit the data type's form markup ("Edit from Markup") and use the above code:
   

   <cms:formdefinition xmlns:cms="http://www.composite.net/ns/management/bindingforms/1.0" xmlns="http://www.composite.net/ns/management/bindingforms/std.ui.controls.lib/1.0" xmlns:f="http://www.composite.net/ns/management/bindingforms/std.function.lib/1.0">
     <cms:bindings>
       <cms:binding name="Id" type="System.Guid" />
       <cms:binding name="SimpleString" type="System.String" />
       <cms:binding name="ParameterizedString" type="System.String" />
       <cms:binding name="KeyValueString" type="System.String" optional="true" />
     </cms:bindings>
     <cms:layout>
       <cms:layout.label>
         <cms:read source="SimpleString" />
       </cms:layout.label>
       <FieldGroup>
         <KeySelector Label="Simple list item field" Help="Populated by a function that returns a List&lt;string&gt;">
           <KeySelector.Selected>
             <cms:bind source="SimpleString" />
           </KeySelector.Selected>
           <KeySelector.Options>
             <f:StaticMethodCall Type="Examples.DataForms.DropDownStrings" Method="GetStrings" />
           </KeySelector.Options>
         </KeySelector>
         <KeySelector Label="Parameterized list item field" Help="Populated by a parameterized function that returns a List&lt;string&gt;">
           <KeySelector.Selected>
             <cms:bind source="ParameterizedString" />
           </KeySelector.Selected>
           <KeySelector.Options>
             <f:StaticMethodCall Type="Examples.DataForms.DropDownStrings" Method="GetStringsWithParameters" Parameters="True" />
           </KeySelector.Options>
         </KeySelector>
         <KeySelector Label="Key value pair field" Help="Populated by a function that returns a Dictionary&lt;string,string&gt;" OptionsKeyField="Key" OptionsLabelField="Value" Required="true">
           <KeySelector.Selected>
             <cms:bind source="KeyValueString" />
           </KeySelector.Selected>
           <KeySelector.Options>
             <f:StaticMethodCall Type="Examples.DataForms.DropDownStrings" Method="GetStringsAsKeyValuePairs" />
           </KeySelector.Options>
         </KeySelector>
       </FieldGroup>
     </cms:layout>
   </cms:formdefinition>