Private Sub Button1_Click(sender As Object, e As System.EventArgs)具有多个带有相同签名的定义

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为什么“Private Sub Button1_Click(sender As Object, e As System.EventArgs)”具有多个带有相同签名的定义。
Imports System.Data.SqlClient '添加引用命名空间
Public Class Tadd
Dim connstr As String = ("Data Source= LAPTOP-IVGA33CA;Initial Catalog=JXGL;Integrated Security=True") '建立连接
Dim conn As New SqlClient.SqlConnection(connstr)
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim insertsql As String = "insert into T(t#,tnametssex,tbirthin,titleof,trsection,tel)"
Dim cmd As New SqlClient.SqlCommand(insertsql, conn)
'检查添加的教师号是否存在
Dim sqlstring As String = "select * from T where t#='" & TextBox1.Text & "' "
conn.Open()
Dim com2 As New SqlClient.SqlCommand(sqlstring, conn)
Dim read1 As SqlDataReader = com2.ExecuteReader
If read1.Read() Then
MsgBox("该教师号已存在！", MsgBoxStyle.Information, "提示！")
TextBox1.Text = ""
TextBox2.Text = ""
ComboBox1.Text = "男"
DateTimePicker1.Value = "1965/12/31"
ComboBox2.Text = ""
ComboBox3.Text = ""
TextBox3.Text = ""
ElseIf TextBox1.Text = "" Then
MsgBox("请输入教师号！", MsgBoxStyle.Information, "提示！")
ElseIf TextBox2.Text = "" Then
MsgBox("请输入姓名！", MsgBoxStyle.Information, "提示！")

Else
'添加新教师的信息
conn.Close()
cmd.Parameters.Add("@T#", SqlDbType.VarChar).Value = TextBox1.Text
cmd.Parameters.Add("@tname", SqlDbType.VarChar).Value = TextBox2.Text
cmd.Parameters.Add("@tsex", SqlDbType.VarChar).Value = ComboBox1.Text
cmd.Parameters.Add("@tbirthin", SqlDbType.VarChar).Value = DateTimePicker1.Value
cmd.Parameters.Add("@titleof", SqlDbType.VarChar).Value = ComboBox2.Text
cmd.Parameters.Add("@trsection", SqlDbType.VarChar).Value = ComboBox3.Text
cmd.Parameters.Add("@tel", SqlDbType.VarChar).Value = TextBox3.Text
conn.Open()
cmd.ExecuteNonQuery()
MsgBox("教师信息添加成功！", MsgBoxStyle.Information, "提示!")
End If
TextBox1.Text = ""
TextBox2.Text = ""
ComboBox1.Text = "男"
DateTimePicker1.Value = "1965/12/31"
ComboBox2.Text = ""
ComboBox3.Text = ""
TextBox3.Text = ""
conn.Close()
End Sub

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Me.Close()
End Sub

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

End Sub
End Class