Control.OnDoubleClick Method
Raises the DoubleClick event.
[Visual Basic] Protected Overridable Sub OnDoubleClick( _ ByVal e As EventArgs _ ) [C#] protected virtual void OnDoubleClick( EventArgs e ); [C++] protected: virtual void OnDoubleClick( EventArgs* e ); [JScript] protected function OnDoubleClick( e : EventArgs );
Parameters
- e
- An EventArgs that contains the event data.
Remarks
Raising an event invokes the event handler through a delegate. For more information, see Raising an Event.
The OnDoubleClick method also allows derived classes to handle the event without attaching a delegate. This is the preferred technique for handling the event in a derived class.
Notes to Inheritors: When overriding OnDoubleClick in a derived class, be sure to call the base class's OnDoubleClick method so that registered delegates receive the event.
Example
[Visual Basic] ' This example uses the DoubleClick event of a ListBox to load text files ' listed in the ListBox into a TextBox control. This example ' assumes that the ListBox, named listBox1, contains a list of valid file ' names with path and that this event handling method ' is connected to the DoublClick event of a ListBox control named listBox1. ' This example requires code access permission to access files. Private Sub listBox1_DoubleClick(ByVal sender As Object, ByVal e As System.EventArgs) Handles listBox1.DoubleClick ' Get the name of the file to open from the ListBox. Dim file As [String] = listBox1.SelectedItem.ToString() Try ' Determine if the file exists before loading. If System.IO.File.Exists(file) Then ' Open the file and use a TextReader to read the contents into the TextBox. Dim myFile As New System.IO.FileInfo(listBox1.SelectedItem.ToString()) Dim myData As System.IO.TextReader = myFile.OpenText() textBox1.Text = myData.ReadToEnd() myData.Close() End If ' Exception is thrown by the OpenText method of the FileInfo class. Catch MessageBox.Show("The file you specified does not exist.") ' Exception is thrown by the ReadToEnd method of the TextReader class. Catch MessageBox.Show("There was a problem loading the file into the TextBox. Ensure that the file is a valid text file.") End Try End Sub [C#] // This example uses the DoubleClick event of a ListBox to load text files // listed in the ListBox into a TextBox control. This example // assumes that the ListBox, named listBox1, contains a list of valid file // names with path and that this event handling method // is connected to the DoublClick event of a ListBox control named listBox1. // This example requires code access permission to access files. private void listBox1_DoubleClick(object sender, System.EventArgs e) { // Get the name of the file to open from the ListBox. String file = listBox1.SelectedItem.ToString(); try { // Determine if the file exists before loading. if (System.IO.File.Exists(file)) { // Open the file and use a TextReader to read the contents into the TextBox. System.IO.FileInfo myFile = new System.IO.FileInfo(listBox1.SelectedItem.ToString()); System.IO.TextReader myData = myFile.OpenText();; textBox1.Text = myData.ReadToEnd(); myData.Close(); } } // Exception is thrown by the OpenText method of the FileInfo class. catch(System.IO.FileNotFoundException) { MessageBox.Show("The file you specified does not exist."); } // Exception is thrown by the ReadToEnd method of the TextReader class. catch(System.IO.IOException) { MessageBox.Show("There was a problem loading the file into the TextBox. Ensure that the file is a valid text file."); } } [C++] // This example uses the DoubleClick event of a ListBox to load text files // listed in the ListBox into a TextBox control. This example // assumes that the ListBox, named listBox1, contains a list of valid file // names with path and that this event handling method // is connected to the DoublClick event of a ListBox control named listBox1. // This example requires code access permission to access files. private: void listBox1_DoubleClick(Object* /*sender*/, System::EventArgs* /*e*/) { // Get the name of the file to open from the ListBox. String* file = listBox1->SelectedItem->ToString(); try { // Determine if the file exists before loading. if (System::IO::File::Exists(file)) { // Open the file and use a TextReader to read the contents into the TextBox. System::IO::FileInfo* myFile = new System::IO::FileInfo(listBox1->SelectedItem->ToString()); System::IO::TextReader* myData = myFile->OpenText();; textBox1->Text = myData->ReadToEnd(); myData->Close(); } } // Exception is thrown by the OpenText method of the FileInfo class. catch(System::IO::FileNotFoundException*) { MessageBox::Show(S"The file you specified does not exist."); } // Exception is thrown by the ReadToEnd method of the TextReader class. catch(System::IO::IOException*) { MessageBox::Show(S"There was a problem loading the file into the TextBox. Ensure that the file is a valid text file."); } }
[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button
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Requirements
Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family
See Also
Control Class | Control Members | System.Windows.Forms Namespace | DoubleClick