如何从后面的 C# 代码更新 WPF 绑定的值？

Question

Used the following piece of code to bind a property on textbox. The property value is getting refreshed while text box value is modified is changed in UI. But I assigned the value to textbox on code behind[txtNoOfSessions.Text = "1"] , but it is not reflecting the value in property.

 <TextBox x:Name="txtNoOfSessions" 
          Text="{Binding Path=NoOfSessions,Mode=TwoWay}" 
          Height="23" Width="120" />

Answer 1

Use INotifyPropertyChanged on the property. Otherwise, it will not update after the UI has loaded.

http://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged.aspx

Example:

public string PhoneNumber
{
    get
    {
        return this.phoneNumberValue;
    }

    set
    {
        if (value != this.phoneNumberValue)
        {
            this.phoneNumberValue = value;
            NotifyPropertyChanged("PhoneNumber");
        }
    }
}

Answer 2

这个答案需要更新或删除。

Answer 3

Usually I try not to update databound values from the code behind the UI, however if I have to I use the DataContext of the UI object and update the bound property.

In your example, it would look something like this:

MyDataObject obj = txtNoOfSessions.DataContext as MyDataObject;
if (obj != null)
    obj.NoOfSessions = "New Value";

Answer 4

Rachel is right, you cannot update bound values directly on the controls without overwriting the binding itself.

You can use the above or ((dynamic)this.DataContext).NoOfSession = "New Value"; is how I do it.

This way, the code will work without knowing the view model type. The view model could even be an ExpandoObject instead of a class and it will still work.

Note that ExpandoObject databinding is broken in Windows Store apps.

https://connect.microsoft.com/VisualStudio/feedback/details/836252/databinding-in-windows-store-apps-to-an-expandoobject-change-notification-not-working

Answer 5

txtNoOfSession.Text is bound. Set the value of the bound property. That is set NoOfSessions in your view model.

NoOfSessions = 1