ToolboxItemFilterAttribute.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / CompMod / System / ComponentModel / ToolboxItemFilterAttribute.cs / 1 / ToolboxItemFilterAttribute.cs
                        

                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.ComponentModel { 
 
    using System;
    using System.Diagnostics; 
    using System.Security.Permissions;

    /// 
    ///     This attribute allows you to configure a filter that is used enable or disable toolbox items 
    ///     from being used on particular designers.  For example, you may have a class of components
    ///     that can only be used on a certain type of designer.  You can configure a toolbox item 
    ///     filter to enforce that rule.  For example, take a report designer that uses a component 
    ///     base class of ReportElement.  You may want to make ReportElement toolbox items enabled only
    ///     when a ReportDesigner is the active designer.  To do this, you would add the following 
    ///     ToolboxItemFilter attributes to each class:
    ///
    ///     [ToolboxItemFilter("MyReportFilterString", ToolboxItemFilterType.Require)]
    ///     public class ReportElement : Component {} 
    ///
    ///     [ToolboxItemFilter("MyReportFilterString", ToolboxItemFilterType.Require)] 
    ///     public class ReportDesigner : Component {} 
    ///
    ///     These two filters specify that ReportElement toolbox items will only be 
    ///     enabled when a ReportDesigner is visible.  By specifying a filter type of
    ///     Require on the report designer class, this will disable any toolbox items
    ///     that are not report elements.  If the report designer specifed a filter type
    ///     of "Allow" instead of "Require", other components would be enabled when the 
    ///     report designer was active.  ReportElements would still be disabled when
    ///     other designers were active, however, because ReportElement requires designers 
    ///     to have the given filter string. 
    ///
    ///     Toolbox item filtering is a useful way to restrict toolbox item visibility to 
    ///     cases where it is appropriate. This can help to avoid confusion for users, but
    ///     you should use caution not to make items unusually restrictive.  If you have a
    ///     general purpose component, for example, you should allow the component to appear
    ///     on any designer. 
    ///
    ///     The ASP.NET and Windows Forms designers both use filter attributes to prevent 
    ///     each other's components from being enabled. This is a useful restriction because, 
    ///     since each has several duplicate class names, it may be confusing to users and
    ///     they may not know which controls to choose. 
    ///
    /// 
    [
    AttributeUsage(AttributeTargets.Class, AllowMultiple=true, Inherited=true), 
    Serializable
    ] 
    public sealed class ToolboxItemFilterAttribute : Attribute { 
        private ToolboxItemFilterType filterType;
        private string                filterString; 
        private string                typeId;

        /// 
        ///     Initializes a new ToolboxItemFilterAttribute with the provide filter string and a filter type of 
        ///     "Allow".
        ///  
        public ToolboxItemFilterAttribute(string filterString) : this(filterString, ToolboxItemFilterType.Allow) { 
        }
 
        /// 
        ///     Initializes a new ToolboxItemFilterAttribute with the provide filter string and filter type.
        /// 
        public ToolboxItemFilterAttribute(string filterString, ToolboxItemFilterType filterType) { 
            if (filterString == null) filterString = String.Empty;
 
            this.filterString = filterString; 
            this.filterType = filterType;
        } 

        /// 
        ///     Retrieves the filter string for this attribute.  The filter string is a user-defined string that
        ///     is used to identify matching attributes. 
        /// 
        public string FilterString { 
            get { 
                return filterString;
            } 
        }

        /// 
        ///     Retrieves the filter type for this attribute.  The filter type determines how the filter string should 
        ///     be applied.
        ///  
        public ToolboxItemFilterType FilterType { 
            get {
                return filterType; 
            }
        }

        ///  
        ///     The unique identifier for this attribute.  All ToolboxItemFilterAttributes with the same filter string
        ///     are considered the same, so they return the same TypeId. 
        ///  
        public override object TypeId {
            get { 
                if (typeId == null) {
                    typeId = GetType().FullName + filterString;
                }
                return typeId; 
            }
        } 
 
        public override bool Equals(object obj) {
            if (obj == this) { 
                return true;
            }

            ToolboxItemFilterAttribute other = obj as ToolboxItemFilterAttribute; 
            return (other != null && other.FilterType.Equals(FilterType) && other.FilterString.Equals(FilterString));
        } 
 
        public override int GetHashCode() {
            // No need to hash on filter type as well; there shouldn't be that many duplicates. 
            return filterString.GetHashCode();
        }

        public override bool Match(object obj) { 

            ToolboxItemFilterAttribute other = obj as ToolboxItemFilterAttribute; 
            if (other == null) { 
                return false;
            } 

            // different filter string kills a match immediately.
            //
            if (!other.FilterString.Equals(FilterString)) { 
                return false;
            } 
 
            return true;
        } 

        public override string ToString() {
            return filterString + "," + Enum.GetName(typeof(ToolboxItemFilterType), filterType);
        } 
    }
}

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