主题：[求助]怎么表达月的第一天

Dim year As WinForm.ComboBox = e.Form.Controls("年")
Dim month As WinForm.ComboBox = e.Form.Controls("月")
Dim csrq As WinForm.DateTimePicker = e.Form.Controls("DateTimePicker1")

Dim FirstDay As Date = New Date(year.Text,1,1) '第一天
Dim LastDay As Date = New Date(year.Text,month.Text,Date.DaysInMonth(year.Text,month.Text)) '最后一天

Dim MDay As Date = New Date(month.Text,1)'月的第一天

Dim MDay As Date = New Date(month.Text,1)'月的第一天

帮我改下代码，这个表示不了