An expression of non-boolean type specified in a context where a condition is expected, near 'AdmissionID'

Server Error in '/' Application.

An expression of non-boolean type specified in a context where a condition is expected, near 'AdmissionID'.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Data.SqlClient.SqlException: An expression of non-boolean type specified in a context where a condition is expected, near 'AdmissionID'.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[SqlException (0x80131904): An expression of non-boolean type specified in a context where a condition is expected, near 'AdmissionID'.]
   System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction) +1767866
   System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction) +5352418
   System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose) +244
   System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady) +1691
   System.Data.SqlClient.SqlDataReader.TryConsumeMetaData() +61
   System.Data.SqlClient.SqlDataReader.get_MetaData() +90
   System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) +365
   System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async, Int32 timeout, Task& task, Boolean asyncWrite, SqlDataReader ds) +1406
   System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean asyncWrite) +177
   System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method) +53
   System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method) +134
   System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior) +41
   System.Data.Common.DbCommand.System.Data.IDbCommand.ExecuteReader(CommandBehavior behavior) +10
   System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +140
   System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +316
   System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, String srcTable) +86
   System.Web.UI.WebControls.SqlDataSourceView.ExecuteSelect(DataSourceSelectArguments arguments) +1481
   System.Web.UI.WebControls.ListControl.OnDataBinding(EventArgs e) +101
   System.Web.UI.WebControls.ListControl.PerformSelect() +34
   System.Web.UI.WebControls.BaseDataBoundControl.DataBind() +30
   System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound() +105
   System.Web.UI.WebControls.BaseDataBoundControl.set_RequiresDataBinding(Boolean value) +9844021
   System.Web.UI.WebControls.DataBoundControl.OnDataSourceViewChanged(Object sender, EventArgs e) +15
   System.Web.UI.DataSourceView.OnDataSourceViewChanged(EventArgs e) +105
   System.Web.UI.WebControls.SqlDataSourceView.SelectParametersChangedEventHandler(Object o, EventArgs e) +31
   System.Web.UI.WebControls.ParameterCollection.OnParametersChanged(EventArgs e) +20
   System.Web.UI.WebControls.Parameter.UpdateValue(HttpContext context, Control control) +142
   System.Web.UI.WebControls.ParameterCollection.UpdateValues(HttpContext context, Control control) +101
   System.Web.UI.WebControls.ParameterCollection.GetValues(HttpContext context, Control control) +36
   System.Web.UI.WebControls.SqlDataSourceView.InitializeParameters(DbCommand command, ParameterCollection parameters, IDictionary exclusionList) +257
   System.Web.UI.WebControls.SqlDataSourceView.ExecuteSelect(DataSourceSelectArguments arguments) +589
   System.Web.UI.WebControls.ListControl.OnDataBinding(EventArgs e) +101
   System.Web.UI.WebControls.ListControl.PerformSelect() +34
   System.Web.UI.WebControls.BaseDataBoundControl.DataBind() +30
   System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound() +105
   System.Web.UI.WebControls.ListControl.OnPreRender(EventArgs e) +23
   System.Web.UI.Control.PreRenderRecursiveInternal() +83
   System.Web.UI.Control.PreRenderRecursiveInternal() +155
   System.Web.UI.Control.PreRenderRecursiveInternal() +155
   System.Web.UI.Control.PreRenderRecursiveInternal() +155
   System.Web.UI.Control.PreRenderRecursiveInternal() +155
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +974

My SQL Command is like this >> SELECT * FROM [Bed] WHERE WardID = @WardID AND BedStatus = 'Available' AND BedNo NOT IN (SELECT BedNo FROM [AdmissionDetail], [Admission] WHERE ([AdmissionDate] <= @AdmissionDate AND [DischargeDate] >= @DischargeDate AND AdmissionStatus <> 'Discharged' AND [AdmissionDetail]AdmissionID = [Admission]AdmissionID))

I'm using Visual Studio 2013 and using asp:DropDownList and asp:SqlDataSource to do this. I have 4 table which is Admission, AdmissionDetail, Ward and Bed.