变量不会增加

Question

Public Class Form2

    Dim i As Integer = 0

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMainMenu.Click
        Me.Close()
    End Sub

    Private Sub btnEnterPatient_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEnterPatient.Click


        ReDim Preserve Names(0 To i)
        Names(i) = txtPatientName.Text

        ReDim Preserve Heights(0 To i)
        Heights(i) = txtPatientHeight.Text

        ReDim Preserve Weights(0 To i)
        Weights(i) = txtPatientWeight.Text

        i = i + 1

    End Sub
End Class

这是我的代码，当我单击按钮将数据输入三个数组时，但是当我单击按钮时i不会增加。此外，如果我没有在高度或重量文本框中输入任何内容并按下按钮，我会收到错误：从字符串“”转换为“整数”类型无效。

这是什么问题？ 感谢