MetadataCache.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / Dotnetfx_Vista_SP2 / Dotnetfx_Vista_SP2 / 8.0.50727.4016 / DEVDIV / depot / DevDiv / releases / Orcas / QFE / ndp / fx / src / DataWeb / Server / System / Data / Services / Caching / MetadataCache.cs / 1 / MetadataCache.cs
                        

                        
                            //---------------------------------------------------------------------- 
// 
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//  
//      Provides a class to cache metadata information.
//  
// 
// @owner  [....]
//--------------------------------------------------------------------- 

namespace System.Data.Services.Caching
{
    using System; 
    using System.Diagnostics;
    using System.Collections.Generic; 
    using System.Threading; 
    using System.Data.Objects;
    using System.Data.Common; 
    using System.Data.EntityClient;

    /// 
    /// Use this class to cache metadata through MetadataCacheItem instances. 
    /// 
    internal static class MetadataCache 
    { 
        /// AppDomain-wide cache for metadata items.
        private static Dictionary cache = new Dictionary(new MetadataCacheKey.Comparer()); 

        /// Reader/writer lock for AppDomain .
        private static ReaderWriterLockSlim cacheLock = new ReaderWriterLockSlim(LockRecursionPolicy.NoRecursion);
 
        /// Adds a new cache item, and returns the item that is put in the cache.
        /// Type of service with metadata being cached. 
        ///  
        /// Data context instance being cached, possibly segmenting the cache
        /// space for . 
        /// 
        /// Item being added.
        /// The item being put in the cache (possibly an existing one).
        /// This method is thread-safe but not re-entrant. 
        internal static MetadataCacheItem AddCacheItem(Type serviceType, object dataContextInstance, MetadataCacheItem item)
        { 
            Debug.Assert(serviceType != null, "serviceType != null"); 
            Debug.Assert(dataContextInstance != null, "dataContextInstance != null");
            Debug.Assert(item != null, "item != null"); 

            MetadataCacheKey key = new MetadataCacheKey(serviceType, dataContextInstance as ObjectContext);
            MetadataCacheItem result;
            cacheLock.EnterWriteLock(); 
            try
            { 
                // If another thread beat the current thread, we return the 
                // previously created item, which has a higher chance of
                // having survived a garbage collection already. 
                if (!cache.TryGetValue(key, out result))
                {
                    cache.Add(key, item);
                    result = item; 
                }
            } 
            finally 
            {
                cacheLock.ExitWriteLock(); 
            }

            Debug.Assert(result != null, "result != null -- a null item is never returned.");
            Debug.Assert( 
                result == TryLookup(serviceType, dataContextInstance),
                "result == TryLookup(serviceType, dataContextInstance) -- instance from cache is being returned."); 
 
            return result;
        } 

        /// Tries to look up metadata for the specifed service type and context instance.
        /// Type of service with metadata being cached.
        ///  
        /// Data context instance being cached, possibly segmenting the cache
        /// space for . 
        ///  
        /// The cached metadata item, if one exists.
        /// This method is thread-safe but not re-entrant. 
        internal static MetadataCacheItem TryLookup(Type serviceType, object dataContextInstance)
        {
            Debug.Assert(serviceType != null, "serviceType != null");
            Debug.Assert(dataContextInstance != null, "dataContextInstance != null"); 

            MetadataCacheKey key = new MetadataCacheKey(serviceType, dataContextInstance as ObjectContext); 
            MetadataCacheItem result; 
            cacheLock.EnterReadLock();
            try 
            {
                cache.TryGetValue(key, out result);
            }
            finally 
            {
                cacheLock.ExitReadLock(); 
            } 

            return result; 
        }

        /// This type is used as the key in the metadata cache.
        internal struct MetadataCacheKey 
        {
            /// Connection string used to segment service type. 
            private readonly string dataContextConnection; 

            /// Hash code for this instance. 
            private readonly int hashCode;

            /// Service type.
            private readonly Type serviceType; 

            /// Initializes a new MetadataCacheKey instance. 
            /// Service type for key. 
            /// Data context instace for key, possibly null.
            internal MetadataCacheKey(Type serviceType, ObjectContext dataContextInstance) 
            {
                Debug.Assert(serviceType != null, "serviceType != null");
                this.serviceType = serviceType;
                this.dataContextConnection = null; 
                this.hashCode = this.serviceType.GetHashCode();
 
                if (dataContextInstance != null) 
                {
                    EntityConnection connection = dataContextInstance.Connection as EntityConnection; 
                    if (connection != null)
                    {
                        this.dataContextConnection = new EntityConnectionStringBuilder(connection.ConnectionString).Metadata;
                        this.hashCode ^= this.dataContextConnection.GetHashCode(); 
                    }
                } 
            } 

            /// Comparer for metadata cache keys. 
            internal class Comparer : IEqualityComparer
            {
                /// Compares the specified keys.
                /// First key. 
                /// Second key.
                /// true if  equals , false otherwise. 
                public bool Equals(MetadataCacheKey x, MetadataCacheKey y) 
                {
                    return x.dataContextConnection == y.dataContextConnection && x.serviceType == y.serviceType; 
                }

                /// Gets the hash code for the object.
                /// Object. 
                /// The hash code for this key.
                public int GetHashCode(MetadataCacheKey obj) 
                { 
                    return obj.hashCode;
                } 
            }
        }
    }
} 


// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
//---------------------------------------------------------------------- 
// 
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//  
//      Provides a class to cache metadata information.
//  
// 
// @owner  [....]
//--------------------------------------------------------------------- 

namespace System.Data.Services.Caching
{
    using System; 
    using System.Diagnostics;
    using System.Collections.Generic; 
    using System.Threading; 
    using System.Data.Objects;
    using System.Data.Common; 
    using System.Data.EntityClient;

    /// 
    /// Use this class to cache metadata through MetadataCacheItem instances. 
    /// 
    internal static class MetadataCache 
    { 
        /// AppDomain-wide cache for metadata items.
        private static Dictionary cache = new Dictionary(new MetadataCacheKey.Comparer()); 

        /// Reader/writer lock for AppDomain .
        private static ReaderWriterLockSlim cacheLock = new ReaderWriterLockSlim(LockRecursionPolicy.NoRecursion);
 
        /// Adds a new cache item, and returns the item that is put in the cache.
        /// Type of service with metadata being cached. 
        ///  
        /// Data context instance being cached, possibly segmenting the cache
        /// space for . 
        /// 
        /// Item being added.
        /// The item being put in the cache (possibly an existing one).
        /// This method is thread-safe but not re-entrant. 
        internal static MetadataCacheItem AddCacheItem(Type serviceType, object dataContextInstance, MetadataCacheItem item)
        { 
            Debug.Assert(serviceType != null, "serviceType != null"); 
            Debug.Assert(dataContextInstance != null, "dataContextInstance != null");
            Debug.Assert(item != null, "item != null"); 

            MetadataCacheKey key = new MetadataCacheKey(serviceType, dataContextInstance as ObjectContext);
            MetadataCacheItem result;
            cacheLock.EnterWriteLock(); 
            try
            { 
                // If another thread beat the current thread, we return the 
                // previously created item, which has a higher chance of
                // having survived a garbage collection already. 
                if (!cache.TryGetValue(key, out result))
                {
                    cache.Add(key, item);
                    result = item; 
                }
            } 
            finally 
            {
                cacheLock.ExitWriteLock(); 
            }

            Debug.Assert(result != null, "result != null -- a null item is never returned.");
            Debug.Assert( 
                result == TryLookup(serviceType, dataContextInstance),
                "result == TryLookup(serviceType, dataContextInstance) -- instance from cache is being returned."); 
 
            return result;
        } 

        /// Tries to look up metadata for the specifed service type and context instance.
        /// Type of service with metadata being cached.
        ///  
        /// Data context instance being cached, possibly segmenting the cache
        /// space for . 
        ///  
        /// The cached metadata item, if one exists.
        /// This method is thread-safe but not re-entrant. 
        internal static MetadataCacheItem TryLookup(Type serviceType, object dataContextInstance)
        {
            Debug.Assert(serviceType != null, "serviceType != null");
            Debug.Assert(dataContextInstance != null, "dataContextInstance != null"); 

            MetadataCacheKey key = new MetadataCacheKey(serviceType, dataContextInstance as ObjectContext); 
            MetadataCacheItem result; 
            cacheLock.EnterReadLock();
            try 
            {
                cache.TryGetValue(key, out result);
            }
            finally 
            {
                cacheLock.ExitReadLock(); 
            } 

            return result; 
        }

        /// This type is used as the key in the metadata cache.
        internal struct MetadataCacheKey 
        {
            /// Connection string used to segment service type. 
            private readonly string dataContextConnection; 

            /// Hash code for this instance. 
            private readonly int hashCode;

            /// Service type.
            private readonly Type serviceType; 

            /// Initializes a new MetadataCacheKey instance. 
            /// Service type for key. 
            /// Data context instace for key, possibly null.
            internal MetadataCacheKey(Type serviceType, ObjectContext dataContextInstance) 
            {
                Debug.Assert(serviceType != null, "serviceType != null");
                this.serviceType = serviceType;
                this.dataContextConnection = null; 
                this.hashCode = this.serviceType.GetHashCode();
 
                if (dataContextInstance != null) 
                {
                    EntityConnection connection = dataContextInstance.Connection as EntityConnection; 
                    if (connection != null)
                    {
                        this.dataContextConnection = new EntityConnectionStringBuilder(connection.ConnectionString).Metadata;
                        this.hashCode ^= this.dataContextConnection.GetHashCode(); 
                    }
                } 
            } 

            /// Comparer for metadata cache keys. 
            internal class Comparer : IEqualityComparer
            {
                /// Compares the specified keys.
                /// First key. 
                /// Second key.
                /// true if  equals , false otherwise. 
                public bool Equals(MetadataCacheKey x, MetadataCacheKey y) 
                {
                    return x.dataContextConnection == y.dataContextConnection && x.serviceType == y.serviceType; 
                }

                /// Gets the hash code for the object.
                /// Object. 
                /// The hash code for this key.
                public int GetHashCode(MetadataCacheKey obj) 
                { 
                    return obj.hashCode;
                } 
            }
        }
    }
} 


// File provided for Reference Use Only by Microsoft Corporation (c) 2007.

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