Missing compiler required member 'microsoft.csharp.runtimebinder.binder.convert'

I first time using Excel to reading data in c# with Selenium WebDriver, but when I build this code, it pops up an error:

"Missing compiler required member 'microsoft.csharp.runtimebinder.binder.convert'"

and the code for using excel is marked in red bellow:

 excel.Application x1Appl = new excel.Application();
 excel.Workbook x1WorkBook = x1Appl.Workbooks.Open(@"C:\app\o\SearchBy.xlsx");

 excel._Worksheet x1WorkSheet = x1WorkBook.Sheets[1];

Please let me know what is missing? Thank you!