PagedDataSource.cs source code in C# .NET

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Code:

                         / DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / xsp / System / Web / UI / WebControls / PagedDataSource.cs / 1 / PagedDataSource.cs
                        

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

namespace System.Web.UI.WebControls { 
 
    using System;
    using System.Collections; 
    using System.ComponentModel;
    using System.Web.UI;
    using System.Security.Permissions;
 

    ///  
    ///    Provides a wrapper over an ICollection datasource to implement paging 
    ///       semantics or 'paged views' on top of the underlying datasource.
    ///  
    [AspNetHostingPermission(SecurityAction.LinkDemand, Level=AspNetHostingPermissionLevel.Minimal)]
    public sealed class PagedDataSource : ICollection, ITypedList {

        private IEnumerable dataSource; 
        private int currentPageIndex;
        private int pageSize; 
        private bool allowPaging; 
        private bool allowCustomPaging;
        private bool allowServerPaging; 
        private int virtualCount;


        ///  
        /// Initializes a new instance of the  class.
        ///  
        public PagedDataSource() { 
            this.pageSize = 10;
            this.allowPaging = false; 
            this.currentPageIndex = 0;
            this.allowCustomPaging = false;
            this.allowServerPaging = false;
            this.virtualCount = 0; 
        }
 
 

        ///  
        ///    Indicates whether to assume the underlying datasource
        ///    contains data for just the current page.
        /// 
        public bool AllowCustomPaging { 
            get {
                return allowCustomPaging; 
            } 
            set {
                allowCustomPaging = value; 
            }
        }

 
        /// 
        ///    Indicates whether to implement page semantics on top of the underlying datasource. 
        ///  
        public bool AllowPaging {
            get { 
                return allowPaging;
            }
            set {
                allowPaging = value; 
            }
        } 
 

        ///  
        /// Indicates whether to implement page semantics on top of the underlying datasource.
        /// 
        public bool AllowServerPaging {
            get { 
                return allowServerPaging;
            } 
            set { 
                allowServerPaging = value;
            } 
        }


        ///  
        ///    
        ///       Specifies the number of items 
        ///       to be used from the datasource. 
        /// 
        public int Count { 
            get {
                if (dataSource == null)
                    return 0;
 
                if (IsPagingEnabled) {
                    if (IsCustomPagingEnabled || (IsLastPage == false)) { 
                        // In custom paging the datasource can contain at most 
                        // a single page's worth of data.
                        // In non-custom paging, all pages except last one have 
                        // a full page worth of data.
                        return pageSize;
                    }
                    else { 
                        // last page might have fewer items in datasource
                        return DataSourceCount - FirstIndexInPage; 
                    } 
                }
                else { 
                    return DataSourceCount;
                }
            }
        } 

 
        ///  
        ///    Indicates the index of the current page.
        ///  
        public int CurrentPageIndex {
            get {
                return currentPageIndex;
            } 
            set {
                currentPageIndex = value; 
            } 
        }
 

        /// 
        ///     Indicates the data source.
        ///  
        public IEnumerable DataSource {
            get { 
                return dataSource; 
            }
            set { 
                dataSource = value;
            }
        }
 

        ///  
        ///  
        public int DataSourceCount {
            get { 
                if (dataSource == null)
                    return 0;
                if (IsCustomPagingEnabled || IsServerPagingEnabled) {
                    return virtualCount; 
                }
                else { 
                    if (dataSource is ICollection) { 
                        return ((ICollection)dataSource).Count;
                    } 
                    else {
                        // The caller should not call this in the case of an IEnumerator datasource
                        // This is required for paging, but the assumption is that the user will set
                        // up custom paging. 
                        throw new HttpException(SR.GetString(SR.PagedDataSource_Cannot_Get_Count));
                    } 
                } 
            }
        } 

        /// 
        /// 
        public int FirstIndexInPage { 
            get {
                if ((dataSource == null) || (IsPagingEnabled == false)) { 
                    return 0; 
                }
                else { 
                    if (IsCustomPagingEnabled || IsServerPagingEnabled) {
                        // In this mode, all the data belongs to the current page.
                        return 0;
                    } 
                    else {
                        return currentPageIndex * pageSize; 
                    } 
                }
            } 
        }


        ///  
        /// 
        public bool IsCustomPagingEnabled { 
            get { 
                return IsPagingEnabled && allowCustomPaging;
            } 
        }


        ///  
        /// 
        public bool IsFirstPage { 
            get { 
                if (IsPagingEnabled)
                    return(CurrentPageIndex == 0); 
                else
                    return true;
            }
        } 

 
        ///  
        /// 
        public bool IsLastPage { 
            get {
                if (IsPagingEnabled)
                    return(CurrentPageIndex == (PageCount - 1));
                else 
                    return true;
            } 
        } 

 
        /// 
        /// 
        public bool IsPagingEnabled {
            get { 
                return allowPaging && (pageSize != 0);
            } 
        } 

 
        /// 
        /// 
        public bool IsReadOnly {
            get { 
                return false;
            } 
        } 

 
        /// 
        /// Indicates whether server-side paging is enabled
        /// 
        public bool IsServerPagingEnabled { 
            get {
                return IsPagingEnabled && allowServerPaging; 
            } 
        }
 

        /// 
        /// 
        public bool IsSynchronized { 
            get {
                return false; 
            } 
        }
 

        /// 
        /// 
        public int PageCount { 
            get {
                if (dataSource == null) 
                    return 0; 

                int dataSourceItemCount = DataSourceCount; 
                if (IsPagingEnabled && (dataSourceItemCount > 0)) {
                    int pageCountNum = dataSourceItemCount + pageSize - 1;
                    if (pageCountNum < 0) {
                        return 1;   // integer overflow 
                    }
                    return (int)(pageCountNum/pageSize); 
                } 
                else {
                    return 1; 
                }
            }
        }
 

        ///  
        ///  
        public int PageSize {
            get { 
                return pageSize;
            }
            set {
                pageSize = value; 
            }
        } 
 

        ///  
        /// 
        public object SyncRoot {
            get {
                return this; 
            }
        } 
 

        ///  
        /// 
        public int VirtualCount {
            get {
                return virtualCount; 
            }
            set { 
                virtualCount = value; 
            }
        } 


        /// 
        ///  
        public void CopyTo(Array array, int index) {
            for (IEnumerator e = this.GetEnumerator(); e.MoveNext();) 
                array.SetValue(e.Current, index++); 
        }
 
        /// 
        /// 
        public IEnumerator GetEnumerator() {
            int startIndex = FirstIndexInPage; 
            int count = -1;
 
            if (dataSource is ICollection) { 
                count = Count;
            } 

            if (dataSource is IList) {
                return new EnumeratorOnIList((IList)dataSource, startIndex, count);
            } 
            else if (dataSource is Array) {
                return new EnumeratorOnArray((object[])dataSource, startIndex, count); 
            } 
            else if (dataSource is ICollection) {
                return new EnumeratorOnICollection((ICollection)dataSource, startIndex, count); 
            }
            else {
                if (allowCustomPaging || allowServerPaging) {
                    // startIndex does not matter 
                    // however count does... even if the data source contains more than 1 page of data in
                    // it, we only want to enumerate over a single page of data 
                    // note: we can call Count here, even though we're dealing with an IEnumerator 
                    //       because by now we have ensured that we're in custom paging mode
                    return new EnumeratorOnIEnumerator(dataSource.GetEnumerator(), Count); 
                }
                else {
                    // startIndex and count don't matter since we're going to enumerate over all the
                    // data (either non-paged or custom paging scenario) 
                    return dataSource.GetEnumerator();
                } 
            } 
        }
 

        /// 
        /// 
        public PropertyDescriptorCollection GetItemProperties(PropertyDescriptor[] listAccessors) { 
            if (dataSource == null)
                return null; 
 
            if (dataSource is ITypedList) {
                return((ITypedList)dataSource).GetItemProperties(listAccessors); 
            }
            return null;
        }
 

        ///  
        ///  
        public string GetListName(PropertyDescriptor[] listAccessors) {
            return String.Empty; 
        }


 
        /// 
        ///  
        private sealed class EnumeratorOnIEnumerator : IEnumerator { 
            private IEnumerator realEnum;
            private int index; 
            private int indexBounds;

            public EnumeratorOnIEnumerator(IEnumerator realEnum, int count) {
                this.realEnum = realEnum; 
                this.index = -1;
                this.indexBounds = count; 
            } 

            public object Current { 
                get {
                    return realEnum.Current;
                }
            } 

            public bool MoveNext() { 
                bool result = realEnum.MoveNext(); 
                index++;
                return result && (index < indexBounds); 
            }

            public void Reset() {
                realEnum.Reset(); 
                index = -1;
            } 
        } 

 
        /// 
        /// 
        private sealed class EnumeratorOnICollection : IEnumerator {
            private ICollection collection; 
            private IEnumerator collectionEnum;
            private int startIndex; 
            private int index; 
            private int indexBounds;
 
            public EnumeratorOnICollection(ICollection collection, int startIndex, int count) {
                this.collection = collection;
                this.startIndex = startIndex;
                this.index = -1; 

                this.indexBounds = startIndex + count; 
                if (indexBounds > collection.Count) { 
                    indexBounds = collection.Count;
                } 
            }

            public object Current {
                get { 
                    return collectionEnum.Current;
                } 
            } 

            public bool MoveNext() { 
                if (collectionEnum == null) {
                    collectionEnum = collection.GetEnumerator();
                    for (int i = 0; i < startIndex; i++)
                        collectionEnum.MoveNext(); 
                }
                collectionEnum.MoveNext(); 
                index++; 
                return (startIndex + index) < indexBounds;
            } 

            public void Reset() {
                collectionEnum = null;
                index = -1; 
            }
        } 
 

 
        /// 
        /// 
        private sealed class EnumeratorOnIList : IEnumerator {
            private IList collection; 
            private int startIndex;
            private int index; 
            private int indexBounds; 

            public EnumeratorOnIList(IList collection, int startIndex, int count) { 
                this.collection = collection;
                this.startIndex = startIndex;
                this.index = -1;
 
                this.indexBounds = startIndex + count;
                if (indexBounds > collection.Count) { 
                    indexBounds = collection.Count; 
                }
            } 

            public object Current {
                get {
                    if (index < 0) { 
                        throw new InvalidOperationException(SR.GetString(SR.Enumerator_MoveNext_Not_Called));
                    } 
                    return collection[startIndex + index]; 
                }
            } 

            public bool MoveNext() {
                index++;
                return (startIndex + index) < indexBounds; 
            }
 
            public void Reset() { 
                index = -1;
            } 
        }


 
        /// 
        ///  
        private sealed class EnumeratorOnArray : IEnumerator { 
            private object[] array;
            private int startIndex; 
            private int index;
            private int indexBounds;

            public EnumeratorOnArray(object[] array, int startIndex, int count) { 
                this.array = array;
                this.startIndex = startIndex; 
                this.index = -1; 

                this.indexBounds = startIndex + count; 
                if (indexBounds > array.Length) {
                    indexBounds = array.Length;
                }
            } 

            public object Current { 
                get { 
                    if (index < 0) {
                        throw new InvalidOperationException(SR.GetString(SR.Enumerator_MoveNext_Not_Called)); 
                    }
                    return array[startIndex + index];
                }
            } 

            public bool MoveNext() { 
                index++; 
                return (startIndex + index) < indexBounds;
            } 

            public void Reset() {
                index = -1;
            } 
        }
    } 
}

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