vb.net中提示将string转换为datetime失败，运行就提示这个，头疼一上午了，求解

Imports System.Data.SqlClient
Public Class Form4
Dim cn As SqlConnection
Dim da As SqlDataAdapter
Dim ds As DataSet
Private Sub Form4_Load（sender As Object， e As EventArgs） Handles MyBase.Load
Dim cnstr As String = "Data Source=(local);initial Catalog=AmusementPark;Integrated Security=true;"
cn = New SqlConnection(cnstr)
da = New SqlDataAdapter("select * from 游客表"， cn)
ds = New DataSet()
da.Fill(ds, "游客表")
DataGridView1.DataSource = ds.Tables("游客表")
TextBox1.Text = ""
TextBox2.Text = ""
TextBox3.Text = ""
TextBox4.Text = ""
TextBox5.Text = ""
TextBox6.Text = ""
End Sub

Private Sub Button10_Click(sender As Object, e As EventArgs) Handles Button10.Click
Me.Hide()
Form2.Show()
End Sub

Private Sub DataGridView1_CellContentClick(sender As Object, e As DataGridViewCellEventArgs) Handles DataGridView1.CellContentClick

End Sub

Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged

End Sub

Private Sub Button7_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button7.Click
If Me.TextBox1.Text <> "" And Me.TextBox2.Text <> "" Then
Dim insert As String
insert = "insert into 游客表(Vid,VName,ID,FP,Pword,Birthdate)"
insert = insert & "values (@ei,@ci,@cc,@zyh,@ce,@cg)"
Call cn.Open()
Dim cmd As New SqlClient.SqlCommand(insert， cn)
cmd.Parameters.Add("@ei", SqlDbType.BigInt).Value = Trim(TextBox1.Text)
cmd.Parameters.Add("@ci", SqlDbType.NVarChar).Value = Trim(TextBox2.Text)
cmd.Parameters.Add("@cc", SqlDbType.Char).Value = Trim(TextBox3.Text)
cmd.Parameters.Add("@zyh", SqlDbType.NVarChar).Value = Trim(TextBox4.Text)
cmd.Parameters.Add("@cg", SqlDbType.Date).Value = Trim(TextBox6.Text)
cmd.Parameters.Add("@ce", SqlDbType.NVarChar).Value = Trim(TextBox5.Text)
Dim v = cmd.ExecuteNonQuery()
MsgBox("添加成功!", MsgBoxStyle.Information, "提示")
Call cn.Close()
Else
MsgBox("游客姓名和编号不能为空!", MsgBoxStyle.Information, "提示")
End If
End Sub

Private Sub Button9_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button9.Click
If Me.TextBox1.Text <> "" And Me.TextBox2.Text <> "" Then
Dim edit As String
edit = "update 游客表 set Vid=@ei,VName=@ci,ID=@cc,FP=@zyh,Pword=@ce,Birthdate=@cg"
edit = edit & " where 姓名='" & Trim(TextBox1.Text) & "'"
Call cn.Open()
Dim cmd As New SqlClient.SqlCommand(edit, cn)
cmd.Parameters.Add("@ei", SqlDbType.BigInt).Value = Trim(TextBox1.Text)
cmd.Parameters.Add("@ci", SqlDbType.NVarChar).Value = Trim(TextBox2.Text)
cmd.Parameters.Add("@cc", SqlDbType.Char).Value = Trim(TextBox3.Text)
cmd.Parameters.Add("@zyh", SqlDbType.NVarChar).Value = Trim(TextBox4.Text)
cmd.Parameters.Add("@cg", SqlDbType.Date).Value = Trim(TextBox6.Text)
cmd.Parameters.Add("@ce", SqlDbType.NVarChar).Value = Trim(TextBox5.Text)
cmd.ExecuteNonQuery()
MsgBox("修改成功!", MsgBoxStyle.Information, "提示")
Call cn.Close()
Else
MsgBox("游客编号和姓名不能为空!", MsgBoxStyle.Information, "提示")
End If
End Sub