Using DataSource with TextBox
I usually program in C ++, so all this DataSource / DataSet / Binding stuff confuses me. Hope you guys can help.
Basically I am writing an editor for an XML based file format (specifically OFX for financial data). I used xsd.exe in my schema to deserialize uploaded files into nice, simple old classes. I found a DataGridView that is brilliant and I can just set its DataSource property to one of the collections I'm interested in (in particular the list of transactions) and when I refer to the values these changes will be reflected in the loaded deserialized file, which I can then serialize on save. But when I want to "display" just a simple string in the TextBox (like the account number), I cannot use this clever method in the TextBoxes, it doesn't seem to have a DataSource member ... Using their Text propertyjust sets the text once and doesn't reflect the changes back to the underlying object, so the save must grab the values from the control first. I would like it to be automatic, as for the DataGridView.
I tried to tinker with DataBindings, but I have no idea what to use as propertyName or dataMember, so I'm not sure if this is what I should be using:
accountNumberTextBox.DataBindings.Add(new Binding("???", myDocument.accountNumber, "???");
Am I missing something really obvious? I hope so!
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What you are missing is what is string
immutable in .NET. Thus, for a binding to make sense, the value string
must be encapsulated by something else. The data binding system then replaces the existing string with a new one when the user enters a value.
Something else that encapsulates string
could be DataTable
either a simple old class that includes change notification. The best way to provide this change notification is to implement an interface INotifyPropertyChanged
.
For example:
public class Document : INotifyPropertyChanged
{
private string _accountNumber;
public string AccountNumber
{
get { return _accountNumber; }
set
{
if (_accountNumber != value)
{
_accountNumber = value;
//this tells the data binding system that the value has changed, so the interface should be updated
OnPropertyChanged("AccountNumber");
}
}
}
//raised whenever a property value on this object changes. The data binding system attaches to this event
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName)
{
var handler = PropertyChanged:
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
So, your data binding will look like this:
var document = ...; //get document from somewhere
//bind the Text property on the TextBox to the AccountNumber property on the Document
textBox1.DataBindings.Add("Text", document, "AccountNumber");
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accountNumberTextBox.DataBindings.Add("Text",
myDocumnt.Tables["your_table"],
"table_field");
Example
DataSet ds = new DataSet("DB");
DataTable dt = new DataTable("myTable");
dt.Columns.Add("Name");
dt.Rows.Add("PP");
dt.Rows.Add("QQ");
ds.Tables.Add(dt);
textBox1.DataBindings.Add("Text", ds.Tables["myTable"], "Name");
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