CODEWITHSUNDEEP
c#wpfvalidationdata-binding
user1768685
user1768685

Reputation:

Using WPF validation

I have a dialog in my project that the user enters some values in and when he hits OK I add an item to my database. I am using Entity Framework, so my adding to database code is something like this:

TransactionItem _item = new TransactionItem();
                _item.DoctorID = (int)cmbDoctor.SelectedValue;
                _item.TransactionCategoryID = (int)_dlg.cmbCat.SelectedValue;
                _item.TransactionMethodID = (int)_dlg.cmbMethod.SelectedValue;
                _item.Amount = int.Parse(_dlg.txtAmount.Text);
                _item.DocumentID = _dlg.txtDocNum.Text;
                _item.Info = _dlg.txtInfo.Text;
                _item.Date = _dlg.dteDate.SelectedDate.ToString();
                _db.TransactionItems.Add(_item);
                _db.SaveChanges();

But the problem is there is nothing to bind and enable validating. I have tried making an empty object in my window and bind text box to it, but it had its own problems and didn't work as expected. I just want to when users enter values or when he hits OK, check if all of fields are valid (for example one of problems was if the user didn't enter any value, it is still valid even though the stringnotnull validator is enabled, but the most important problem was that it automatically set the textbox's text to null and mark it as a null value).

And I have made my own validator and here is a example of how I implemented them on one of my textboxes:

<TextBox Name="txtAmount" HorizontalAlignment="Left" Height="23" Margin="83,169,0,0" VerticalAlignment="Top" Width="224" Tag="T">
    <TextBox.Text>
        <Binding  Path="myitem" ElementName="myWindow" UpdateSourceTrigger="PropertyChanged">
            <Binding.ValidationRules>
                <Validators:StringNullValidationRule/>
                <Validators:IsNumericValidationRule/>
            </Binding.ValidationRules>
        </Binding>
    </TextBox.Text>
</TextBox>

Upvotes: 2

Views: 183

Answers (2)

xargs
xargs

Reputation: 3079

Use the IDataErrorInfo interface. You can implement it in your ViewModel or your Model class depending on your design. An example of how you can do it is in WPF: Validation made easy with IDataErrorInfo.

And I recommend you read this great Josh Smith article: WPF Apps With The Model-View-ViewModel Design Pattern. There you can see a good example of validation.

Upvotes: 1

Adi Lester
Adi Lester

Reputation: 25211

Why don't you create a property in your viewmodel for each value the user needs to enter, and bind to it? Then you could use these properties when adding an item. For example:

ViewModel:

public int Amount { get; set; }

...

public void AddItem()
{
    TransactionItem _item = new TransactionItem();

    // ...

    _item.Amount = Amount;
}

XAML:

<TextBox Name="txtAmount" HorizontalAlignment="Left" Height="23" Margin="83,169,0,0" VerticalAlignment="Top" Width="224" Tag="T">
    <TextBox.Text>
        <Binding Path="DataContext.Amount" ElementName="myWindow">
            <Binding.ValidationRules>
                <Validators:StringNullValidationRule/>
                <Validators:IsNumericValidationRule/>
            </Binding.ValidationRules>
        </Binding>
    </TextBox.Text>
</TextBox>

I also recommend having a look at the INotifyDataErrorInfo interface (or the IDataErrorInfo interface if you're using .NET 4.0 or lower) to implement validations.

Upvotes: 1

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