Question

I’m creating a simple code generator with delegates.

Why am I getting this error at runtime:

Error while binding the target method.

on the following code?

XAML:

<Window x:Class='Parser.Window1'     xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation'     xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'         Loaded='Window_Loaded'     Title='Parser' Height='600' Width='800'>          <TextBox x:Name='Output'                  VerticalScrollBarVisibility='Visible'                  Margin='10'/> </Window> 

Code-Behind:

using System; using System.Collections.Generic; using System.Text; using System.Windows;  namespace Parser {     public partial class Window1 : Window     {         private List<string> _fields;          public Window1()         {             InitializeComponent();         }          private void Window_Loaded(object sender, RoutedEventArgs e)         {             _fields = new List<string> { 'CustomerID',                  'CompanyName',                 'ContactName',                 'ContactTitle',                 'Address',                 'City',                 'Region',                 'PostalCode',                 'Country',                 'Phone',                 'Fax'             };              Output.Text += ParseFieldsWithMethod('BuildAssignmentLines');             Output.Text += ParseFieldsWithMethod('BuildEnabledLines');         }          private string ParseFieldsWithMethod(string theParseMethod)         {             Predicate<string> predicate = (Predicate<string>)Delegate.CreateDelegate(typeof(Predicate<string>),                 typeof(Window1).GetMethod(theParseMethod));              StringBuilder sb = new StringBuilder();             foreach (var field in _fields)             {                 sb.Append(predicate.Invoke(field));             }             return sb.ToString();         }          public string BuildAssignmentLines(string field)         {             return String.Format('customer.{0} = Field_{0}.Text;\n', field);         }          public string BuildEnabledLines(string field)         {             return String.Format('Field_{0}.IsEnabled = false;\n', field);         }      } } 

Answer 1

Predicate is a function that takes a string as a parameter and returns a boolean. Yours return strings.

You should use Function instead of Predicate.

Also, you should really send the function as a parameter and not by name.

ParseFieldsWithMethod(x => BuildAssignmentLines(x)); ParseFieldsWithMethod(x => BuildEnabledLines(x));   private string ParseFieldsWithMethod(Func<string, string > parseMethod) {             StringBuilder sb = new StringBuilder();             foreach (var field in _fields)             {                 sb.Append(parseMethod(field));             }             return sb.ToString();         }