我的代码是这样的
Public Declare Function CalcBillMac Lib "CalculateBillMac.dll" (ByVal str As String) As String
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Dim Str_test, XX As String
Str_test = "abcd1234"
Try
XX = Me.CalcBillMac(Str_test)
Me.TextBox3.Text = XX
Catch ex As Exception
Throw ex
End Try