• Article

HtmlWindow.Eval Method

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Evaluates a string that contains arbitrary JavaScript code.

Namespace:  System.Windows.Browser
Assembly:  System.Windows.Browser (in System.Windows.Browser.dll)

Syntax

'Declaration
<SecuritySafeCriticalAttribute> _
Public Function Eval ( _
    code As String _
) As Object

[SecuritySafeCriticalAttribute]
public Object Eval(
    string code
)

Parameters

Return Value

Type: System.Object
The results of the JavaScript engine's evaluation of the string in the code parameter.

Exceptions

Exception Condition
ArgumentNullException

code is nulla null reference (Nothing in Visual Basic).
ArgumentException

code is an empty string.
InvalidOperationException

An unexpected error occurred.

Remarks

The Eval method passes the specified code to the browser's JavaScript engine to parse and execute. If a return value is created as a result, it is marshaled back to managed code by using the heuristics described in Passing JavaScript Objects to Managed Code. The return value follows the same restrictions and conventions as the ScriptObject.Invoke method.

The Firefox and Safari browsers do not propagate errors that occur as a result of calling the Eval method. If you require error information in Firefox or Safari, you should include custom error handling in the code parameter. For example, the following code example permits error information to be marshaled back to managed code.

HtmlPage.Window.Eval("try { //do some work here }
                      catch (e) { e.message ? e.message : e; }"
                    );

Version Information

Silverlight

Supported in: 5, 4, 3

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.