输入一个年、月、日，判断该日是该年的第多少天？用VB.NET程序怎么写

Dim strDate As String
Dim datInput As Date
Dim datFirst As Date
Console.WriteLine("输入日期：")
strDate = Console.ReadLine()
Try
datInput = Date.Parse(strDate)
Catch ex As Exception
Console.WriteLine("输入错误")
Exit Sub
End Try
datFirst = Date.Parse(datInput.Year & "/01/01")
Console.WriteLine(DateDiff(DateInterval.Day, datFirst, datInput))

数学必修三的题目~