How to Set TextBox.Text Value while TextBox bind with MVVM in WPF

Question

I am using WPF forms and i want to know how to set TextBox.Text value though TextBox bind With MVVM. For Example: TextBox.Text = "Hello"; I want to set this value to Text box and my text box like

 public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        txtCityName.Text = "Hello Vaibhav";
        this.DataContext = new MyTesting();

    }
}

My WPF Window Form Class:

Next My Xaml:

 <Grid>
    <TextBox Name="txtCityName" Grid.Row="3" Grid.Column="1"   Text="{Binding CityName, UpdateSourceTrigger=PropertyChanged}" Height="40" Width="200"/>
</Grid>

And Next My Model:

internal class MyTesting : INotifyPropertyChanged
{
    private string _CityName;

    public MyTesting()
    {

    }
    public string CityName
    {
        get { return _CityName; }
        set { _CityName = value; OnPropertyChanged("CityName"); }
    }

    #region PropertyChangedEventHandler
    public event PropertyChangedEventHandler PropertyChanged;
    public void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
    #endregion
    #region " RaisePropertyChanged Function "
    /// <summary>
    /// 
    /// </summary>
    /// <param name="propertyName"></param>
    private void RaisePropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new System.ComponentModel.PropertyChangedEventArgs(propertyName));

    }
    #endregion
}

But NULL assigned to TextBox . How to solve this

check VS Output window for binding exceptions. make sure that you set DataContext. Code provided at the moment is not enough to reproduce the issue, please create a minimal complete example — ASh, Aug 10 '17 at 07:16
Is this will work for both as either Set direct value to text value or set value from MVVM. For Example sometimes i want to set TextBox.Text Value like txtCityName.Text="Hello" and sometimes i want it set to be from MVVM — Vaibhav Srivastava, Aug 10 '17 at 07:27
I Updated My Question With Complete Code please look and try and Give me Solution. — Vaibhav Srivastava, Aug 10 '17 at 09:37

tabby · Answer 1 · 2017-08-10T09:11:12.383

7

Try this:

class AddressModel: INotifyPropertyChanged
{
        private string _cityName;
        public string CityName 
        {
        get {
              return _cityName; 
            }
        set {
              _cityName = value; 
              OnPropertyChanged("CityName");
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
        public void OnPropertyChanged(string property)
        {
            this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(property));
        }                           
}

And in your Code Behind:

AddressModel addressModel = new AddressModel();
addressModel.CityName = "YourCity";
this.dataContext = addressModel;

Xaml:

<TextBox Name="txtCityName" Grid.Row="3" Grid.Column="1" Text="{Binding CityName,UpdateSourceTrigger=PropertyChanged}">

edited Aug 10 '17 at 09:11

answered Aug 10 '17 at 07:36

tabby

1,878
1
21
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I can do this but i don't want to set like this i want to set txtCityName.Text = "YourCity" like this. How i can achieve this – Vaibhav Srivastava Aug 10 '17 at 07:52
changing TextBox value using txtCityName.Text = "YourCity" will change your dataContext CityName property Value. so whats the problem? – tabby Aug 10 '17 at 08:35
Problem is that .its not working. Value null assigned to TextBox – Vaibhav Srivastava Aug 10 '17 at 08:45
Yes . Above i gave you the code. I wanted to set TextBox value of two type one i can set from MVVM and Second Directly assign like txtCityName.Text = "YourCity". tHis thing i want to achieve – Vaibhav Srivastava Aug 10 '17 at 08:54
//My Constructor. public UcCountrySetup(int CountryCode, bool isCountryCode) { string codeValue = Convert.ToString(CountryCode); this.DataContext = new AddressViewModel(model); BindFieldData(codeValue); } } – Vaibhav Srivastava Aug 10 '17 at 08:56
Above is my constructor and inside BinFieldData(codeValue). – Vaibhav Srivastava Aug 10 '17 at 08:57
txtCityName.Text ="YourCity; – Vaibhav Srivastava Aug 10 '17 at 08:57
the code above has to work make sure to add UpdateSourceTrigger=PropertyChanged in your TextBox – tabby Aug 10 '17 at 09:13
how to write in textbox i getting error.i wrote like -> – Vaibhav Srivastava Aug 10 '17 at 09:28
You should set the CityName source property. See my answer. – mm8 Aug 10 '17 at 09:32
This is Not Working i tried. public partial class MainWindow : Window { public MainWindow() { InitializeComponent(); txtCityName.Text = "Hello Ishir"; this.DataContext = new MyTesting(); } } – Vaibhav Srivastava Aug 10 '17 at 09:34
I Updated My Question With Complete Code please look and try and Give me Solution. – Vaibhav Srivastava Aug 10 '17 at 09:37
Set this value txtCityName.Text = "Hello Ishir" in Loaded event and it will change the datacontext CityName property value as well – tabby Aug 10 '17 at 09:52

score 0 · Accepted Answer · answered Aug 10 '17 at 09:32

0

txtCityName.Text = "YourCity" is not MVVM.

You should set the CityName source property instead of setting the Text property of the TextBox control.

<TextBox Name="txtCityName" Grid.Row="3" Grid.Column="1" Text="{Binding CityName}">

this.DataContext = new AddressModel();

AddressModel obj = this.DataContext as AddressModel;
obj.CityName = "..."; //<--this will update the data-bound TextBox

answered Aug 10 '17 at 09:32

mm8

163,881
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This is the only problem i can not set like this i can only want to set like txtCityName.Text = ".." – Vaibhav Srivastava Aug 10 '17 at 09:33
I need a view model. Both Scenario is different text box should be set with both while using view model or while using .Text. – Vaibhav Srivastava Aug 10 '17 at 09:38
I Updated My Question With Complete Code please look and try and Give me Solution. – Vaibhav Srivastava Aug 10 '17 at 09:38
I have already told you that you need to set the value of the source property. – mm8 Aug 10 '17 at 09:42
did you check my given code please use complete code and check what is coming i want to set value by using TextBox.Text Property – Vaibhav Srivastava Aug 10 '17 at 09:49
Set the binding mode to OneWayToSource. But then you won't be able update the TextBlock from the view model. It is one way or the other, not both. Basic MVVM. – mm8 Aug 10 '17 at 09:51
How can i know on Run time that TextBox bind with which MVVM Property. Is there any way? – Vaibhav Srivastava Aug 10 '17 at 10:46
That's a totally different question. Please don't ask additional questions in the comments field. Ask a bew question if you have another issue. – mm8 Aug 10 '17 at 11:51
Actually Its related to this question only. Because if i can not assign value to .Text property then i want to know which MVVm Property add with this TextBox and i can assign that value to that property in Run time – Vaibhav Srivastava Aug 10 '17 at 11:53
Yes. Thank you . You save my time – Vaibhav Srivastava Aug 10 '17 at 12:37

How to Set TextBox.Text Value while TextBox bind with MVVM in WPF

2 Answers2