如何防止锁定行。插入有效，但更新无效

Question

我的代码问题是我可以正确插入数据库，但如果它会更新，则连接超时。因此，为了澄清我的问题，我的INSERT代码可以正常工作，但UPDATE并没有。 我已经使用过sql事务，因此数据仍然被锁定，我无法更新。

这是我的代码：

Protected Sub btnSave_Click(sender As Object, e As EventArgs) Handles btnSave.Click
    Dim strConnString As String = DataSource.ConnectionString
    Using con As New SqlConnection(strConnString)
        Dim SQLStr As String

        Dim base64String = TextArea1.Value
        Dim imageBytes As Byte() = Convert.FromBase64String(base64String)
        Dim FileSizeOfIMG As String
        FileSizeOfIMG = imageBytes.Length
        Dim ImageTypeDataOfImage As New SqlParameter("@Data", SqlDbType.Image)
        ImageTypeDataOfImage.Value = imageBytes

        SQLStr = "SELECT 1 FROM [Patient_Data].[dbo].[tbPatientImage]   where HospNum='" & Session.Item("HospNum") & "' and IDNum='" & Session.Item("IDNum") & "' and FileType= '" & lblHeader.Text & "'"

        Dim cmd As New SqlCommand(SQLStr, con)
        cmd.Connection = con
        con.Open()
        Dim transaction As SqlTransaction

        transaction = con.BeginTransaction("MyTransaction")
        cmd.Transaction = transaction
        Dim reader As SqlDataReader = cmd.ExecuteReader()

        If reader.Read() Then
            SQLStr = "UPDATE [Patient_Data].[dbo].[tbPatientImage] SET PatImage= @Data, FileSize= '" & FileSizeOfIMG.ToString & "' , TransDate = GetDate() where HospNum='" & Session.Item("HospNum") & "' and IDNum='" & Session.Item("IDNum") & "' and FileType= '" & lblHeader.Text & "'  "
        Else

            SQLStr = "INSERT INTO [Patient_Data].[dbo].[tbPatientImage](HospNum,IDNum, DoctorID, PatImage , FileType, FileName, FileSize , TransDATE) " & _
                    " VALUES ('" & Session.Item("HospNum") & "','" & Session.Item("IDNum") & "', '" & Session.Item("DoctorID") & "', @Data, '" & lblHeader.Text & "', 'PatientPhoto' , '" & FileSizeOfIMG.ToString & "',  GETDATE())"
        End If
        reader.Close()
        cmd.CommandText = SQLStr
        cmd.Parameters.Add(ImageTypeDataOfImage)
        transaction.Commit()
        cmd.ExecuteNonQuery()
        con.Close()
        GetData()
    End Using
End Sub