C# – How to bind column header to property in ViewModel? (WPF MVVM)

cdatacontextdatagridmvvmwpf

I Have window that have DataContext that is bind to ViewModel object (VM1 for the example).
VM1 have a lot of properties and one of them is a string that called "MyTitle".

I have a DataGridTextColumn in 'Window\Grid\DataGrid'. How can I bind the property "Header" in DataGridTextColumn to the Property "MyTitle" in my VM1 ViewModel?

Thanks!

Best Answer

Unfortunately, the column definitions of the DataGrid don't inherit the DataContext, because they're not part of the visual tree, so you can't bind directly to the ViewModel. You need to resort to a workaround such as the one described in this article:

<DataGrid.Resources>
    <local:BindingProxy x:Key="proxy" Data="{Binding}" />
</DataGrid.Resources>

...

<DataGridTextColumn Header="{Binding Data.MyTitle, Source={StaticResource proxy}}"/>

Related Solutions

Wpf – INotifyPropertyChanged vs. DependencyProperty in ViewModel

Kent wrote an interesting blog about this topic: View Models: POCOs versus DependencyObjects.

Short summary:

DependencyObjects are not marked as serializable
The DependencyObject class overrides and seals the Equals() and GetHashCode() methods
A DependencyObject has thread affinity – it can only be accessed on the thread on which it was created

I prefer the POCO approach. A base class for PresentationModel (aka ViewModel) which implements INotifyPropertyChanged interface can be found here: http://compositeextensions.codeplex.com

C# – String representation of an Enum

Try type-safe-enum pattern.

public sealed class AuthenticationMethod {

    private readonly String name;
    private readonly int value;

    public static readonly AuthenticationMethod FORMS = new AuthenticationMethod (1, "FORMS");
    public static readonly AuthenticationMethod WINDOWSAUTHENTICATION = new AuthenticationMethod (2, "WINDOWS");
    public static readonly AuthenticationMethod SINGLESIGNON = new AuthenticationMethod (3, "SSN");        

    private AuthenticationMethod(int value, String name){
        this.name = name;
        this.value = value;
    }

    public override String ToString(){
        return name;
    }

}

Update Explicit (or implicit) type conversion can be done by

adding static field with mapping
```
private static readonly Dictionary<string, AuthenticationMethod> instance = new Dictionary<string,AuthenticationMethod>();
```
- n.b. In order that the initialisation of the the "enum member" fields doesn't throw a NullReferenceException when calling the instance constructor, be sure to put the Dictionary field before the "enum member" fields in your class. This is because static field initialisers are called in declaration order, and before the static constructor, creating the weird and necessary but confusing situation that the instance constructor can be called before all static fields have been initialised, and before the static constructor is called.
filling this mapping in instance constructor
```
instance[name] = this;
```

and adding user-defined type conversion operator

public static explicit operator AuthenticationMethod(string str)
{
    AuthenticationMethod result;
    if (instance.TryGetValue(str, out result))
        return result;
    else
        throw new InvalidCastException();
}

Best Answer

Related Solutions

Wpf – INotifyPropertyChanged vs. DependencyProperty in ViewModel

C# – String representation of an Enum

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