C# OpenFileDialog Example

Use the OpenFileDialog control in Windows Forms to enable the selection of a file.

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OpenFileDialog. This allows users to browse folders and select files. It can be used with C# code. It displays the standard Windows dialog box. The results of the selection can be read in your C# code.SaveFileDialog

ShowDialog. You can open the OpenFileDialog that is in your Windows Forms program. The dialog will not open automatically and it must be invoked in your custom code. You will want to use an event handler to open the dialog in your C# code.
Button: You can add a Button control. Find the Button icon in the Toolbox and drag it to an area in your Windows Forms window.
Tip: You can add an event to the button click by double-clicking on the "button1" in the designer.
Here: This DialogResult variable is tested to see what action the user specified to take.
C# program that uses OpenFileDialog using System; using System.Windows.Forms; namespace WindowsFormsApplication1 { public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void button1_Click(object sender, EventArgs e) { // Show the dialog and get result. DialogResult result = openFileDialog1.ShowDialog(); if (result == DialogResult.OK) // Test result. { } Console.WriteLine(result); // <-- For debugging use. } } }

Read files. You can access the file specified by the user in the OpenFileDialog—and then read it in using the System.IO namespace methods. We also handle exceptions, preventing some errors related to file system changes that are unavoidable.
Note: In this example, when you click on the button the dialog will ask you what file you want.
And: When you accept the dialog, the code will read in that file and print its size in bytes.
C# program that reads in file from OpenFileDialog using System; using System.IO; using System.Windows.Forms; namespace WindowsFormsApplication1 { public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void button1_Click(object sender, EventArgs e) { int size = -1; DialogResult result = openFileDialog1.ShowDialog(); // Show the dialog. if (result == DialogResult.OK) // Test result. { string file = openFileDialog1.FileName; try { string text = File.ReadAllText(file); size = text.Length; } catch (IOException) { } } Console.WriteLine(size); // <-- Shows file size in debugging mode. Console.WriteLine(result); // <-- For debugging use. } } }

Properties. The OpenFileDialog control in Windows Forms has many properties that you can set directly in the designer. You do not need to assign them in your own C# code. This section shows some notes on these properties.
AddExtension: You can change this to False from its default True if you want to automatically fix file extension problems.
AutoUpgradeEnabled: This allows you to automatically get Vista-style open file dialogs. It is recommended.
DefaultExt: Set this to a string extension for files to automatically add that extension. This is not often useful.
DereferenceLinks: This tells Windows to resolve shortcuts (aliases) on the system before returning the paths.
FileName: You can initialize this in the designer to a preset file name. This is changed to be the name the user specifies.
InitialDirectory: Specify a string to use that folder as the starting point. Try using Environment.SpecialFolder with this property.
Multiselect: Specifies if multiple files can be selected at once in the dialog. Users can select multiple files by holding SHIFT or CTRL.

Filter. Filters make it easier for the user to open a valid file. The OpenFileDialog supports filters for matching file names. The asterisk indicates a wildcard. With an extension, you can filter by a file type.
Filter: Use this to specify the file matching filter for the dialog box. With "C# files|*.cs", only files ending with ".cs" are shown.
FilterIndex: Use to specify the default filter, which will have index of 1. The second filter if one exists would have index of 2.
ValidateNames: The Windows file system does not allow files to contain characters such as "*". This option should usually be left as True.

ReadOnly. To continue, the OpenFileDialog has some properties that allow users to specify whether a file should be read in read-only mode. The read-only checkbox can be displayed. Usually these are not needed.

Summary. We looked at the useful OpenFileDialog in Windows Forms. Nearly every nontrivial program will need to have an open file dialog. This control implements this functionality without any problems.


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