WPF Textbox accept INT but not NULLABLE INT?

Question

Model

public int? SizeLength { get; set; }

XAML

<TextBox Text="{Binding [someViewModel].SizeLength, Mode=TwoWay}"></TextBox>

Once user try to backspace or delete the value in this textbox, a message Value '' cannot be converted.

May I know what's wrong with it?

score 35 · Accepted Answer · answered Feb 15 '14 at 04:02

35

Use:

{Binding TargetNullValue=''}

answered Feb 15 '14 at 04:02

I tried `` as well as ``..Both still throwing the same error – SuicideSheep Feb 15 '14 at 07:13
3

@Mr.SuicideSheep - You need to set it to empty string as mentioned in answer and not to 0. – Rohit Vats Feb 15 '14 at 07:16

score 4 · Answer 2 · edited Mar 09 '17 at 15:21

Since the integrated converters from string to single/double/int of WPF are expecting a string to parse they won't default the null value to 0 because you won't always want that behavior, so as it is written in MSDN :

Gets or sets the value that is used in the target when the value of the source is null.

you use this to define your default value for null input:

{Binding TargetNullValue=''}

TargetNullValue msdn

score 0 · Answer 3 · answered Nov 26 '14 at 14:44

You need to add a reference of mscorlib in your XAML, Nullable or ? in your prop and use TargetNullValue with value "" like Elios said.

xmlns:sys="clr-namespace:System;assembly=mscorlib"

public Nullable<int> Prop { get; set; }

{Binding prop, TargetNullValue=''}

WPF Textbox accept INT but not NULLABLE INT?

3 Answers3