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Covariance and Contravariance (C#) https://docs.microsoft.com/en-us/dotnet/articles/csharp/programming-guide/concepts/covariance-contravariance/ In C# 阅读全文
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未处理System.InvalidCastException HResult=-2147467262 Message=无法将类型为“Microsoft.Office.Interop.Excel.ApplicationClass”的 COM 对象强制转换为接口类型“Microsoft.Office... 阅读全文