public class Hashtable : Dictionary<object, object> {}

This method combines the functionality of the ContainsKey method and the Item property.

If the key is not found, then the value parameter gets the appropriate default value for the value type TValue; for example, 0 (zero) for integer types, false for Boolean types, and nullNothingnullptra null reference (Nothing in Visual Basic) for reference types.

Use the TryGetValue method if your code frequently attempts to access keys that are not in the dictionary. Using this method is more efficient than catching the KeyNotFoundException thrown by the Item property.

This method approaches an O(1) operation.

        static TestService()
        {
            SetPermissions("Customers", DataSourceRights.Read, "CustomerId", "FirstName", "LastName");
            SetPermissions("Orders", DataSourceRights.Read|DataSourceRights.Write);
        }

        private static readonly Dictionary<string, TablePermissions> DataSecurity = new Dictionary<string, TablePermissions>();

        public static Func<string, string, bool> DemandFieldPermission = (tableName, fieldName) =>
                                                {
                                                    TablePermissions tablePermissions;
                                                    if (!DataSecurity.TryGetValue(tableName, out tablePermissions))
                                                        return false;
                                                    return tablePermissions.Fields==null || tablePermissions.Fields.Contains(fieldName);
                                                };

        public static Func<string, DataSourceRights, bool> DemandTablePermission = (tableName, rights) =>
                                                {
                                                    TablePermissions tablePermissions;
                                                    if (!DataSecurity.TryGetValue(tableName,out tablePermissions))
                                                        return false;
                                                    return (tablePermissions.Rights & rights) != 0;
                                                };

        protected static void SetPermissions(string tableName, DataSourceRights dataSourceRights, params string[] fields)
        {
            DataSecurity.Add(tableName,
                             new TablePermissions
                                 {
                                     TableName = tableName,
                                     Rights = dataSourceRights,
                                     Fields = fields == null ? null : new List<string>(fields)
                                 });
        }

                    case (int)QueryElementType.SqlTable :
                        {
                            var sourceID           = ReadInt();
                            var name               = ReadString();
                            var alias              = ReadString();
                            var database           = ReadString();
                            var owner              = ReadString();
                            var physicalName       = ReadString();
                            var objectType         = Read<Type>();
                            var sequenceAttributes = null as SequenceNameAttribute[];
#if !SILVERLIGHT
                            if (!LinqService.DemandTablePermission(name, demandingPermission))
                                throw new SecurityAccessDeniedException(string.Format("{0} access denied for {1}", demandingPermission, alias));
#endif

CREATE PROCEDURE [dbo].[ImageTag::CreateInstance](
    @SecurityContext UNIQUEIDENTIFIER,
    @ID UNIQUEIDENTIFIER,
    @Format INT,
    @Family NVARCHAR(16),
    @Data VARBINARY(MAX),
    @Target_Type UNIQUEIDENTIFIER,
    @Target_ID UNIQUEIDENTIFIER)
AS
BEGIN
    DECLARE @SecurityResult INT;

    EXECUTE @SecurityResult = [~EmployeePermissions::Check] @SecurityContext, '37caf5e2-4128-415f-9dbb-01322ec06f0a', NULL, 1;

    IF @SecurityResult = 0
        RAISERROR (N'ACCESS DENIED;ImageTag;CreateInstance', 16, 0);

    INSERT INTO
        [ImageTag]([ID], [Format], [Family], [Data], [Target/Type], [Target/ID])
    VALUES
        (@ID, @Format, @Family, @Data, @Target_Type, @Target_ID);
END

CREATE PROCEDURE [dbo].[ImageTag::ReadAllInstances](
    @SecurityContext UNIQUEIDENTIFIER)
AS
BEGIN
    DECLARE @SecurityResult INT;
    DECLARE @DefaultPermissions INT;

    EXECUTE @SecurityResult = [~EmployeePermissions::Check] @SecurityContext, '37caf5e2-4128-415f-9dbb-01322ec06f0a', NULL, 2048;

    IF @SecurityResult = 0
    BEGIN
        SET @DefaultPermissions = 0
    END
    ELSE
    BEGIN
        SET @DefaultPermissions = 2048
    END

    SELECT
        [ID],
        [Format],
        [Family],
        [Data],
        [Target/Type],
        [Target/ID]
    FROM
        [ImageTag]
    WHERE
        (@DefaultPermissions = 2048)
END

CREATE PROCEDURE [dbo].[Account::ReadAllInstances](
    @SecurityContext UNIQUEIDENTIFIER)
AS
BEGIN
    DECLARE @SecurityResult INT;
    DECLARE @DefaultPermissions INT;

    EXECUTE @SecurityResult = [~EmployeePermissions::Check] @SecurityContext, '0e490d07-556d-41c4-86aa-0689dee1c98a', NULL, 2048;

    IF @SecurityResult = 0
    BEGIN
        SET @DefaultPermissions = 0
    END
    ELSE
    BEGIN
        SET @DefaultPermissions = 2048
    END

    SELECT
        [ID],
        [HierarchyID],
        [HierarchyLevel],
        [HierarchyParent],
        [Code],
        [Name],
        [Employee],
        [Family],
        [Organization]
    FROM
        [Account]
    LEFT OUTER JOIN
        [~EmployeePermissions] ON [~EmployeePermissions].[~Target] = [Account].[ID]
    WHERE
        (ISNULL([~EmployeePermissions].[~Permissions], @DefaultPermissions) & 2048) <> 0
END

IT>using (var host = new ServiceHost(new LinqService(), new Uri("net.tcp://localhost:1234")))
IT>{
.....

IT>    var list = ctx.GetTable<Person>().ToList();

........
IT>}
IT>

System.ServiceModel.Dispatcher.NetDispatcherFaultException was unhandled
Message=The formatter threw an exception while trying to deserialize the message: There was an error while trying to deserialize parameter http://tempuri.org/:ExecuteReaderResult. The InnerException message was 'There was an error deserializing the object of type BLToolkit.ServiceModel.LinqServiceResult. The maximum string content length quota (8192) has been exceeded while reading XML data. This quota may be increased by changing the MaxStringContentLength property on the XmlDictionaryReaderQuotas object used when creating the XML reader.'. Please see InnerException for more details.
Source=mscorlib
Action=http://schemas.microsoft.com/net/2005/12/windowscommunicationfoundation/dispatcher/fault
StackTrace:
Server stack trace:
at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.DeserializeParameterPart(XmlDictionaryReader reader, PartInfo part, Boolean isRequest)
at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.DeserializeParameter(XmlDictionaryReader reader, PartInfo part, Boolean isRequest)
at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.DeserializeBody(XmlDictionaryReader reader, MessageVersion version, String action, MessageDescription messageDescription, Object[] parameters, Boolean isRequest)
at System.ServiceModel.Dispatcher.OperationFormatter.DeserializeBodyContents(Message message, Object[] parameters, Boolean isRequest)
at System.ServiceModel.Dispatcher.OperationFormatter.DeserializeReply(Message message, Object[] parameters)
at System.ServiceModel.Dispatcher.ProxyOperationRuntime.AfterReply(ProxyRpc& rpc)
at System.ServiceModel.Channels.ServiceChannel.HandleReply(ProxyOperationRuntime operation, ProxyRpc& rpc)
at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)
Exception rethrown at [0]:
at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
at BLToolkit.ServiceModel.ILinqService.ExecuteReader(LinqServiceQuery query)
at BLToolkit.ServiceModel.LinqServiceClient.ExecuteReader(LinqServiceQuery query) in d:\GeneratedCode\9\Test\BLToolkit\ServiceModel\LinqServiceClient.cs:line 43
at BLToolkit.ServiceModel.ServiceModelDataContext.BLToolkit.Data.Linq.IDataContext.ExecuteReader(Object query) in d:\GeneratedCode\9\Test\BLToolkit\ServiceModel\ServiceModelDataContext.cs:line 210
at BLToolkit.Data.Linq.Query`1.<RunQuery>d__2a.MoveNext() in d:\GeneratedCode\9\Test\BLToolkit\Data\Linq\Query.cs:line 367
at BLToolkit.Data.Linq.Query`1.<Map>d__32.MoveNext() in d:\GeneratedCode\9\Test\BLToolkit\Data\Linq\Query.cs:line 383
at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
at Program.Main() in D:\GeneratedCode\9\Test\Test\Program.cs:line 106
at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
InnerException: System.Runtime.Serialization.SerializationException
Message=There was an error deserializing the object of type BLToolkit.ServiceModel.LinqServiceResult. The maximum string content length quota (8192) has been exceeded while reading XML data. This quota may be increased by changing the MaxStringContentLength property on the XmlDictionaryReaderQuotas object used when creating the XML reader.
Source=System.Runtime.Serialization
StackTrace:
at System.Runtime.Serialization.XmlObjectSerializer.ReadObjectHandleExceptions(XmlReaderDelegator reader, Boolean verifyObjectName, DataContractResolver dataContractResolver)
at System.Runtime.Serialization.DataContractSerializer.ReadObject(XmlDictionaryReader reader, Boolean verifyObjectName)
at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.DeserializeParameterPart(XmlDictionaryReader reader, PartInfo part, Boolean isRequest)
InnerException: System.Xml.XmlException
Message=The maximum string content length quota (8192) has been exceeded while reading XML data. This quota may be increased by changing the MaxStringContentLength property on the XmlDictionaryReaderQuotas object used when creating the XML reader.
Source=System.Runtime.Serialization
LineNumber=0
LinePosition=0
StackTrace:
at System.Xml.XmlExceptionHelper.ThrowXmlException(XmlDictionaryReader reader, String res, String arg1, String arg2, String arg3)
at System.Xml.XmlExceptionHelper.ThrowMaxStringContentLengthExceeded(XmlDictionaryReader reader, Int32 maxStringContentLength)
at System.Xml.XmlDictionaryReader.ReadContentAsString(Int32 maxStringContentLength)
at System.Xml.XmlBaseReader.ReadContentAsString()
at System.Xml.XmlBaseReader.ReadElementContentAsString()
at System.Xml.XmlBinaryReader.ReadElementContentAsString()
at System.Runtime.Serialization.XmlReaderDelegator.ReadElementContentAsString()
at ReadLinqServiceResultFromXml(XmlReaderDelegator , XmlObjectSerializerReadContext , XmlDictionaryString[] , XmlDictionaryString[] )
at System.Runtime.Serialization.ClassDataContract.ReadXmlValue(XmlReaderDelegator xmlReader, XmlObjectSerializerReadContext context)
at System.Runtime.Serialization.XmlObjectSerializerReadContext.ReadDataContractValue(DataContract dataContract, XmlReaderDelegator reader)
at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator reader, String name, String ns, Type declaredType, DataContract& dataContract)
at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator xmlReader, Type declaredType, DataContract dataContract, String name, String ns)
at System.Runtime.Serialization.DataContractSerializer.InternalReadObject(XmlReaderDelegator xmlReader, Boolean verifyObjectName, DataContractResolver dataContractResolver)
at System.Runtime.Serialization.XmlObjectSerializer.ReadObjectHandleExceptions(XmlReaderDelegator reader, Boolean verifyObjectName, DataContractResolver dataContractResolver)
InnerException:

var binding = new NetTcpBinding(SecurityMode.None)
{
    MaxReceivedMessageSize = 10000000,
    MaxBufferPoolSize      = 10000000,
    MaxBufferSize          = 10000000,
    CloseTimeout           = new TimeSpan(00, 01, 00),
    OpenTimeout            = new TimeSpan(00, 01, 00),
    ReceiveTimeout         = new TimeSpan(00, 10, 00),
    SendTimeout            = new TimeSpan(00, 10, 00),
};

binding.ReaderQuotas.MaxStringContentLength = Int32.MaxValue;

using (var host = new ServiceHost(new LinqService(), new Uri("net.tcp://localhost:1234")))
{
    host.Description.Behaviors.Add(new ServiceMetadataBehavior());
    host.Description.Behaviors.Find<ServiceDebugBehavior>().IncludeExceptionDetailInFaults = true;
    host.AddServiceEndpoint(typeof(IMetadataExchange), MetadataExchangeBindings.CreateMexTcpBinding(), "mex");
    host.AddServiceEndpoint(
        typeof(ILinqService),
        new NetTcpBinding(SecurityMode.None)
        {
            MaxReceivedMessageSize = 10000000,
            MaxBufferPoolSize      = 10000000,
            MaxBufferSize          = 10000000,
            CloseTimeout           = new TimeSpan(00, 01, 00),
            OpenTimeout            = new TimeSpan(00, 01, 00),
            ReceiveTimeout         = new TimeSpan(00, 10, 00),
            SendTimeout            = new TimeSpan(00, 10, 00),
        },
        "LinqOverWCF");

    host.Open();

    var ctx = new ServiceModelDataContext(
        new NetTcpBinding(SecurityMode.None)
        {
            MaxReceivedMessageSize = 10000000,
            MaxBufferPoolSize      = 10000000,
            MaxBufferSize          = 10000000,
            CloseTimeout           = new TimeSpan(00, 01, 00),
            OpenTimeout            = new TimeSpan(00, 01, 00),
            ReceiveTimeout         = new TimeSpan(00, 10, 00),
            SendTimeout            = new TimeSpan(00, 10, 00),
        },
        new EndpointAddress("net.tcp://localhost:1234/LinqOverWCF"));

    var list = ctx.GetTable<Person>().ToList();

    host.Close();

    return list;
}