WPF TargetNullValue returning value when the textbox's binding is set to OneWayToSource

Question

I have this xaml textbox

<TextBox Text="{Binding ProdFilter.Min, Mode=OneWayToSource,
   UpdateSourceTrigger=PropertyChanged, TargetNullValue=''}"
   Width="50" DockPanel.Dock="Right" TabIndex="3" />

binded to this this property:

        public double? Min
        {
            get { return min; }
            set
            {
                if (value == null)
                    value = 0;
                min = value;
                OnPropertyChanged("Min");
            }
        }

The problem I have is that when the program starts or when there user clears the text, the textbox's text is set to "0". I don't know if this behaviour is right, because i'm using OneWayToSource, but i'd like my property to be set to null when text is empty (and the text to remain empty!)

Any ideas? Thanks!

I don't understand your property. Why use a nullable `double` when you don't allow it to be set to `null`? Why not just use a normal `double`? — Daniel Hilgarth, Mar 01 '11 at 15:59
now i'm using a normal double... can't remember what crossed my mind that day, hahaha! — Martín Coll, Mar 04 '11 at 00:10

score 6 · Accepted Answer · edited May 23 '17 at 12:26

6

This is because WPF re-reads the value from the property after it sets it even though the binding is OneWayToSource. Please see the answer to this question for possible workaround.

edited May 23 '17 at 12:26

Community

1
1

answered Mar 01 '11 at 15:58

Pavlo Glazkov

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On a side note, this behavior was introduced in .NET 4.0 – Fredrik Hedblad Mar 01 '11 at 16:01
@Meleak - Yeah, thanks for the great question I'm referring to :) – Pavlo Glazkov Mar 01 '11 at 16:02

WPF TargetNullValue returning value when the textbox's binding is set to OneWayToSource

1 Answers1