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AllowPartiallyTrustedCallersAttribute Class

Allows strong-named assemblies to be called by partially trusted code. Without this declaration, only fully trusted callers are able to use such assemblies. This class cannot be inherited.

Namespace:  System.Security
Assembly:  mscorlib (in mscorlib.dll)

[AttributeUsageAttribute(AttributeTargets.Assembly, AllowMultiple = false, 
	Inherited = false)]
public sealed class AllowPartiallyTrustedCallersAttribute : Attribute

AllowPartiallyTrustedCallersAttribute is only effective when applied by a strong-named assembly at the assembly level. For more information about applying attributes at the assembly level, see Applying Attributes.

By default, a strong-named assembly that does not explicitly apply this attribute at assembly level to allow its use by partially trusted code can be called only by other assemblies that are granted full trust by security policy. This restriction is enforced by placing a LinkDemand for FullTrust on every public or protected method on every publicly accessible class in the assembly. Assemblies that are intended to be called by partially trusted code can declare their intent through the use of the AllowPartiallyTrustedCallersAttribute. The attribute is declared at the assembly level. An example of the declaration in C# is [assembly:AllowPartiallyTrustedCallers] and in Visual Basic is <assembly:AllowPartiallyTrustedCallers>.

Caution noteCaution:

The presence of this assembly-level attribute prevents the default behavior of placing FullTrust  LinkDemand security checks, making the assembly callable from any other assembly (partially or fully trusted).

When this attribute is present, all other security checks function as intended, including any class-level or method-level declarative security attributes that are present. This attribute blocks only the implicit fully trusted caller demand.

This is not a declarative security attribute, but a regular attribute (it derives from Attribute, not SecurityAttribute).

For more information, see Using Libraries from Partially Trusted Code.

The following example shows the use of the AllowPartiallyTrustedCallersAttribute class.

// The following HTML code can be used to call the user control in this sample. 
//	<BODY> 
//		<OBJECT id="usercontrol" classid="usercontrol.dll#UserControl.UserControl1" width="800" 
//		height="300" style="font-size:12;">
//		</OBJECT> 
//		<p> 
//	</BODY> 

// To run this test control you must create a strong name key, snkey.snk, and  
// a code group that gives full trust to assemblies signed with snkey.snk. 

// The user control displays an OpenFileDialog box, then displays a text box containing the name of  
// the file selected and a list box that displays the contents of the file.  The selected file must  
// contain text in order for the control to display the data properly. 

// Caution  This sample demonstrates the use of the Assert method.  Calling Assert removes the  
// requirement that all code in the call chain must be granted permission to access the specified  
// resource, it can open up security vulnerabilities if used incorrectly or inappropriately. Therefore,  
// it should be used with great caution.  Assert should always be followed with a RevertAssert  
// command to restore the security settings. 

using System;
using System.Collections;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Windows.Forms;
using System.IO;
using System.Security;
using System.Security.Permissions;
using System.Reflection;
using System.Runtime.CompilerServices;

// This strong name key is used to create a code group that gives permissions to this assembly.
[assembly: AssemblyKeyFile("snKey.snk")]
[assembly: AssemblyVersion("")]

// The AllowPartiallyTrustedCallersAttribute requires the assembly to be signed with a strong name key. 
// This attribute is necessary since the control is called by either an intranet or Internet 
// Web page that should be running under restricted permissions.
namespace UserControl
	// The userControl1 displays an OpenFileDialog box, then displays a text box containing the name of  
	// the file selected and a list box that displays the contents of the file.  The selected file must  
	// contain text in order for the control to display the data properly. 
	public class UserControl1 : System.Windows.Forms.UserControl
		private System.Windows.Forms.TextBox textBox1;
		private System.Windows.Forms.ListBox listBox1;
		// Required designer variable. 
		private System.ComponentModel.Container components = null;

              // Demand the zone requirement for the calling application.
              [ZoneIdentityPermission(SecurityAction.Demand, Zone = SecurityZone.Intranet)]
		public UserControl1()
			// This call is required by the Windows.Forms Form Designer.

			// The OpenFileDialog box should not require any special permissions.
			OpenFileDialog fileDialog = new OpenFileDialog();
			if(fileDialog.ShowDialog() == DialogResult.OK)
				// Reading the name of the selected file from the OpenFileDialog box 
				// and reading the file requires FileIOPermission.  The user control should  
				// have this permission granted through its code group; the Web page that calls the  
				// control should not have this permission.  The Assert command prevents a stack walk  
				// that would fail because the caller does not have the required FileIOPermission.   
				// The use of Assert can open up security vulnerabilities if used incorrectly or  
				// inappropriately. Therefore, it should be used with great caution. 
				// The Assert command should be followed by a RevertAssert as soon as the file operation  
				// is completed. 
				new FileIOPermission(PermissionState.Unrestricted).Assert();
				textBox1.Text = fileDialog.FileName;
				// Display the contents of the file in the text box.
				FileStream fsIn = new FileStream(textBox1.Text, FileMode.Open, FileAccess.Read, 
				StreamReader sr = new StreamReader(fsIn);
				// Process every line in the file 
				for (String Line = sr.ReadLine(); Line != null; Line = sr.ReadLine()) 
				// It is very important to call RevertAssert to restore the stack walk for 
				// file operations.


		// Clean up any resources being used. 
		protected override void Dispose( bool disposing )
			if( disposing )
				if( components != null )
			base.Dispose( disposing );

		#region Component Designer generated code
		/// <summary> 
		/// Required method for Designer support - do not modify  
		/// the contents of this method with the code editor. 
		/// </summary> 
		private void InitializeComponent()
			this.textBox1 = new System.Windows.Forms.TextBox();
			this.listBox1 = new System.Windows.Forms.ListBox();
			// textBox1 
			this.textBox1.Location = new System.Drawing.Point(208, 112);
			this.textBox1.Name = "textBox1";
			this.textBox1.Size = new System.Drawing.Size(320, 20);
			this.textBox1.TabIndex = 0;
			this.textBox1.Text = "textBox1";
			this.textBox1.TextChanged += new System.EventHandler(this.textBox1_TextChanged);
			// listBox1 
			this.listBox1.Location = new System.Drawing.Point(200, 184);
			this.listBox1.Name = "listBox1";
			this.listBox1.Size = new System.Drawing.Size(336, 108);
			this.listBox1.TabIndex = 1;
			// UserControl1 
			this.Name = "UserControl1";
			this.Size = new System.Drawing.Size(592, 400);
			this.Load += new System.EventHandler(this.UserControl1_Load);


		private void UserControl1_Load(object sender, System.EventArgs e)

		private void textBox1_TextChanged(object sender, System.EventArgs e)



Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0
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