Unexpected error: An item with the same key has already been added.

[rida_wahid]

Hello, I have been trying to load 2 tabls from a DB. One of the table has been loaded successfully but the other table is giving the following error:

Details:
Microsoft.Mashup.Evaluator.Interface.ErrorException: An item with the same key has already been added. ---> System.ArgumentException: An item with the same key has already been added. ---> System.ArgumentException: An item with the same key has already been added.
at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
at Microsoft.Internal.DictionaryTracing.AddWithTracing[K,V](IDictionary`2 dictionary, K key, V value, IEngineHost host, Boolean keyIsPii, Boolean valueIsPii)
at Microsoft.Mashup.Engine1.Library.Common.DbEnvironment.RetrieveKeysForTable(String schemaName, String tableName, Keys columnNames)
at Microsoft.Mashup.Engine1.Library.Common.QueryResultTableTypeValue.get_TableKeys()
at Microsoft.Mashup.Engine1.Runtime.TableTypeValue.GetPrimaryKey()
at Microsoft.Mashup.Engine1.Runtime.TypeValue.get_KeyColumnNames()
at Microsoft.Mashup.Evaluator.ITableSourceSerializationExtensions.WriteITableSource(BinaryWriter writer, ITableSource tableSource)
at Microsoft.Mashup.Evaluator.BinarySerializer.Serialize(Action`1 serializer)
at Microsoft.Mashup.Evaluator.Interface.BufferedMessage.Prepare()
at Microsoft.Mashup.Evaluator.ChannelMessenger.PostWithoutFlowControl(MessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.RemotePreviewValueSource.<>c__DisplayClass5.<RunStub>b__3()
at Microsoft.Mashup.Evaluator.EvaluationHost.ReportExceptions(IHostTrace trace, IEngineHost engineHost, IMessageChannel channel, Action action)
--- End of inner exception stack trace ---
at Microsoft.Mashup.Evaluator.EvaluationHost.<>c__DisplayClass7.<TryReportException>b__6()
at Microsoft.Mashup.Common.SafeExceptions.IgnoreSafeExceptions(IEngineHost host, IHostTrace trace, Action action)
at Microsoft.Mashup.Evaluator.EvaluationHost.TryReportException(IHostTrace trace, IEngineHost engineHost, IMessageChannel channel, Exception exception)
at Microsoft.Mashup.Evaluator.EvaluationHost.ReportExceptions(IHostTrace trace, IEngineHost engineHost, IMessageChannel channel, Action action)
at Microsoft.Mashup.Evaluator.RemotePreviewValueSource.RunStub(IEngineHost engineHost, IMessageChannel channel, Func`1 getPreviewValueSource)
at Microsoft.Mashup.Evaluator.RemoteDocumentEvaluator.Service.<>c__DisplayClass1e`1.<OnBeginGetResult>b__1b()
at Microsoft.Mashup.Evaluator.EvaluationHost.ReportExceptions(IHostTrace trace, IEngineHost engineHost, IMessageChannel channel, Action action)
at Microsoft.Mashup.Evaluator.RemoteDocumentEvaluator.Service.OnBeginGetResult[T](IMessageChannel channel, BeginGetResultMessage message, Action`1 action)
at Microsoft.Mashup.Evaluator.RemoteDocumentEvaluator.Service.OnBeginGetPreviewValueSource(IMessageChannel channel, BeginGetPreviewValueSourceMessage message)
at Microsoft.Mashup.Evaluator.MessageHandlers.TryDispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.ChannelMessenger.ChannelMessageHandlers.TryDispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.MessageHandlers.Dispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.ChannelMessenger.OnMessageWithUnknownChannel(IMessageChannel baseChannel, MessageWithUnknownChannel messageWithUnknownChannel)
at Microsoft.Mashup.Evaluator.MessageHandlers.TryDispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.ChannelMessenger.ChannelMessageHandlers.TryDispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.MessageHandlers.Dispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.EvaluationHost.Run()
at Microsoft.Mashup.Evaluator.SafeThread2.<>c__DisplayClass15.<CreateAction>b__14(Object o)
at Microsoft.Mashup.Container.EvaluationContainerMain.SafeRun(String[] args)
at Microsoft.Mashup.Container.EvaluationContainerMain.Main(String[] args)
--- End of inner exception stack trace ---
at Microsoft.Mashup.Evaluator.EvaluationHost.OnException(IEngineHost engineHost, IMessageChannel channel, ExceptionMessage message)
at Microsoft.Mashup.Evaluator.MessageHandlers.TryDispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.MessageHandlers.Dispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.ChannelMessenger.ChannelMessageHandlers.TryDispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.MessageHandlers.Dispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.Interface.IMessageChannelExtensions.WaitFor[T](IMessageChannel channel)
at Microsoft.Mashup.Evaluator.RemotePreviewValueSource.PreviewValueSource.WaitFor(Func`1 condition, Boolean disposing)
at Microsoft.Mashup.Evaluator.RemotePreviewValueSource.PreviewValueSource.get_TableSource()
at Microsoft.Mashup.Evaluator.Interface.TracingPreviewValueSource.get_TableSource()
at Microsoft.Mashup.Host.Document.Analysis.PackageDocumentAnalysisInfo.PackagePartitionAnalysisInfo.SetPreviewValue(EvaluationResult2`1 result, Func`1 getStaleSince, Func`1 getSampled)

[reganvecera]

I too encountered this error even when trying to load just one table into a blank report. In my case, the solution was some the the automatic detection features Power BI was using. To turn them off go to File > Options > Data Load > uncheck 'Import relationships from data sources on first load'

[rida_wahid · Accepted solution]

The issue is resolved. I had 2 tables in mysql with same name spelling, the only difference was that first tables name started with a capital letter and the other one was all lower caps. This caused a clash in Power BI.