共用方式為

Immediate window

  • 發行項

Applies to: yesVisual Studio noVisual Studio for Mac

Note

This article applies to Visual Studio 2017. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here

Use the Immediate window to debug and evaluate expressions, execute statements, and print variable values. The Immediate window evaluates expressions by building and using the currently selected project.

To display the Immediate window, open a project for editing, and then choose Debug > Windows > Immediate or press Ctrl+Alt+I. You can also enter Debug.Immediate in the Command window.

The Immediate window supports IntelliSense.

Display the values of variables

The Immediate window is particularly useful when you're debugging an app. For example, to check the value of a variable varA, you can use the Print command:

>Debug.Print varA

The question mark (?) is an alias for Debug.Print, so this command can also be written:

? varA

Both versions of this command return the value of the variable varA.

Tip

To issue a Visual Studio command in the Immediate window, you must preface the command with a greater than sign (>). To enter multiple commands, switch to the Command window.

Design-time expression evaluation

You can use the Immediate window to execute a function or subroutine at design time.

Execute a function at design time

  1. Copy the following code into a Visual Basic console app:

    Module Module1

    Sub Main()
        MyFunction(5)
    End Sub

    Function MyFunction(ByVal input as Integer) As Integer
        Return input * 2
    End Function

End Module

  2. On the Debug menu, choose Windows > Immediate.

  3. Type ?MyFunction(2) in the Immediate window and press Enter.

    The Immediate window runs MyFunction and displays 4.

If the function or subroutine contains a breakpoint, Visual Studio breaks execution at the appropriate point. You can then use the debugger windows to examine your program state. For more information, see Walkthrough: Debugging at Design Time.

You can't use design-time expression evaluation in project types that require starting up an execution environment, including Visual Studio Tools for Office projects, web projects, Smart Device projects, and SQL projects.

Design-time expression evaluation in multi-project solutions

When establishing the context for design-time expression evaluation, Visual Studio references the currently selected project in Solution Explorer. If no project is selected in Solution Explorer, Visual Studio attempts to evaluate the function against the startup project. If the function cannot be evaluated in the current context, you'll receive an error message. If you're attempting to evaluate a function in a project that's not the startup project for the solution and you receive an error, try selecting the project in Solution Explorer and attempt the evaluation again.

Enter commands

Enter the greater than sign (>) when issuing Visual Studio commands in the Immediate window. Use the Up arrow and Down arrow keys to scroll through your previously used commands.

Task Solution Example
Evaluate an expression. Preface the expression with a question mark (?). ? a+b
Temporarily enter Command mode while in Immediate mode (to execute a single command). Enter the command, prefacing it with a greater than sign (>). >alias
Switch to the Command window. Enter cmd into the window, prefacing it with a greater than sign (>). >cmd
Switch back to the Immediate window. Enter immed into the window without the greater than sign (>). immed

Mark mode

When you click on any previous line in the Immediate window, you shift automatically into Mark mode. This allows you to select, edit, and copy the text of previous commands as you would in any text editor, and paste them into the current line.

Examples

The following example shows four expressions and their result in the Immediate window for a Visual Basic project.

j = 2
Expression has been evaluated and has no value

? j
2

j = DateTime.Now.Day
Expression has been evaluated and has no value

? j
26

First-chance exception notifications

In some settings configurations, first-chance exception notifications are displayed in the Immediate window.

Toggle first-chance exception notifications in the Immediate window

  1. On the View menu, click Other Windows, and click Output.

  2. Right-click on the text area of the Output window, and then select or deselect Exception Messages.

See also