Excel Destination Error: Column"xx" cannot convert between unicode and nonunicode string data types

If we using 'OLE DB Source' component to obtain the data source and export to the Excel File.

The convert exception will be catch when column is varchar. 

So we can change the varchar to nvarchar or using a 'Data Convertor' component to convert.

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However. I got a other problem. 

In the 'OLE DB Source' component

I selected the Data access mode to 'SQL command' not 'Table or view'.

When I running the SSIS packge and it's passed but the data was not export to Excel file.

Finally I selected the Data access mode to 'Table or view' to solving the problem.