Getting errors with Parameterized Update Sub - tsql

Question

No idea why this isn't working.
I have a simple form with some text boxes and drop down lists. It displays the profile of an employee. Users should be able to manually edit the fields and click Save. When they click save I keep getting errors.
Q1: How can I handle inserting Null values for SmallDateTime data types?
Q2: What am I doing wrong with the TinyInt (SqlServer 2005) on the JobGrade?
Option Explicit On
Imports System
Imports System.Data
Imports System.Data.SqlClient
Protected Sub btnSave_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSave.Click
Dim sqlJobsDB As New SqlConnection(ConfigurationManager.ConnectionStrings("JobsDB").ConnectionString)
Dim sqlCmdUpdate As SqlCommand = sqlJobsDB.CreateCommand()
Try
sqlJobsDB.Open()
sqlCmdUpdate.CommandText = _
"UPDATE tblEmployee " + _
"SET Firstname = #Firstname, LastName = #LastName, HiredLastName = #HiredLastName, " + _
"DateHired = #DateHired, Role = #Role, CADate = #CADate, CAType = #CAType, " + _
"JobDate = #JobDate, JobGrade = #JobGrade " + _
"WHERE EUID = '" & Session("sProfileEUID") & "';"
sqlCmdUpdate.Parameters.Add("#FirstName", SqlDbType.VarChar)
sqlCmdUpdate.Parameters.Add("#LastName", SqlDbType.VarChar)
sqlCmdUpdate.Parameters.Add("#HiredLastName", SqlDbType.VarChar)
sqlCmdUpdate.Parameters.Add("#DateHired", SqlDbType.SmallDateTime)
sqlCmdUpdate.Parameters.Add("#Role", SqlDbType.VarChar)
sqlCmdUpdate.Parameters.Add("#CADate", SqlDbType.SmallDateTime)
sqlCmdUpdate.Parameters.Add("#CAType", SqlDbType.VarChar)
sqlCmdUpdate.Parameters.Add("#JobDate", SqlDbType.SmallDateTime)
sqlCmdUpdate.Parameters.Add("#JobGrade", SqlDbType.TinyInt)
sqlCmdUpdate.Parameters("#FirstName").Value = txtFirstName.Text
sqlCmdUpdate.Parameters("#LastName").Value = txtLastName.Text
sqlCmdUpdate.Parameters("#HiredLastName").Value = txtHiredLastName.Text
sqlCmdUpdate.Parameters("#DateHired").Value = txtDateHired.Text
sqlCmdUpdate.Parameters("#Role").Value = ddlRole.SelectedValue.ToString
If txtCADate.Text = "" Then
sqlCmdUpdate.Parameters("#CADate").Value = 0
Else
sqlCmdUpdate.Parameters("#CADate").Value = txtCADate.Text
End If
sqlCmdUpdate.Parameters("#CAType").Value = ddlCAType.SelectedValue
If txtJobDate.Text = "" Then
sqlCmdUpdate.Parameters("#JobDate").Value = 0
Else
sqlCmdUpdate.Parameters("#JobDate").Value = txtJobDate.Text
End If
sqlCmdUpdate.Parameters("#JobGrade").Value = CByte(txtJobGrade.Text)
sqlCmdUpdate.ExecuteNonQuery()
Catch ex As Exception
'Debugging
lblErrMsg.Text = ex.ToString
lblErrMsg.Visible = True
Finally
sqlJobsDB.Close()
End Try
End Sub</code>
I open the form and fill it out correctly.
I'll enter something like "4" (no quotes) for JobGrade. It still says "conversion from strink ''" like its not even seeing when I input items on the form.
Errors are below:
System.InvalidCastException: Conversion from string "" to type 'Byte' is not valid. ---> System.FormatException: Input string was not in a correct format. at Microsoft.VisualBasic.CompilerServices.Conversions.ParseDouble(String Value, NumberFormatInfo NumberFormat) at Microsoft.VisualBasic.CompilerServices.Conversions.ToByte(String Value) --- End of inner exception stack trace --- at Microsoft.VisualBasic.CompilerServices.Conversions.ToByte(String Value) at Profile.btnSave_Click(Object sender, EventArgs e) in
Update
The DBNull.Value issue is resolved.
The JobGrade, and Role are still issues. When throwing up some breakpoints on it doens't fetch the contents of the textbox or the dropdown list.
** Updated Code **
Protected Sub btnCancel_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnCancel.Click
Session("sProfileEUID") = Nothing
Response.Redirect("~/Management/EditUsers.aspx")
End Sub
Protected Sub btnSave_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSave.Click
Dim sqlJobsDB As New SqlConnection(ConfigurationManager.ConnectionStrings("JobsDB").ConnectionString)
Dim sqlCmdUpdate As SqlCommand = sqlJobsDB.CreateCommand()
Try
sqlJobsDB.Open()
sqlCmdUpdate.CommandText = _
"UPDATE tblEmployee " + _
"SET FirstName = #FirstName, LastName = #LastName, HiredLastName = #HiredLastName, " + _
"DateHired = #DateHired, Role = #Role, CADate = #CADate, CAType = #CAType, " + _
"JobDate = #JobDate, JobGrade = #JobGrade " + _
"WHERE EUID = '" & Session("sProfileEUID") & "';"
sqlCmdUpdate.Parameters.Add("#FirstName", SqlDbType.VarChar)
sqlCmdUpdate.Parameters.Add("#LastName", SqlDbType.VarChar)
sqlCmdUpdate.Parameters.Add("#HiredLastName", SqlDbType.VarChar)
sqlCmdUpdate.Parameters.Add("#DateHired", SqlDbType.SmallDateTime)
sqlCmdUpdate.Parameters.Add("#Role", SqlDbType.VarChar)
sqlCmdUpdate.Parameters.Add("#CADate", SqlDbType.SmallDateTime)
sqlCmdUpdate.Parameters.Add("#CAType", SqlDbType.VarChar)
sqlCmdUpdate.Parameters.Add("#JobDate", SqlDbType.SmallDateTime)
sqlCmdUpdate.Parameters.Add("#JobGrade", SqlDbType.TinyInt)
sqlCmdUpdate.Parameters("#FirstName").Value = txtFirstName.Text
sqlCmdUpdate.Parameters("#LastName").Value = txtLastName.Text
sqlCmdUpdate.Parameters("#HiredLastName").Value = txtHiredLastName.Text
sqlCmdUpdate.Parameters("#DateHired").Value = txtDateHired.Text
sqlCmdUpdate.Parameters("#Role").Value = ddlRole.SelectedValue.ToString
If txtCADate.Text <> "" Then sqlCmdUpdate.Parameters("#CADate").Value = CDate(txtCADate.Text)
If txtCADate.Text = "" Then sqlCmdUpdate.Parameters("#CADate").Value = DBNull.Value
If ddlCAType.Text <> "" Then sqlCmdUpdate.Parameters("#CAType").Value = ddlCAType.SelectedValue
If ddlCAType.Text = "" Then sqlCmdUpdate.Parameters("#CAType").Value = DBNull.Value
If txtJobDate.Text <> "" Then sqlCmdUpdate.Parameters("#JobDate").Value = CDate(txtJobDate.Text)
If txtJobDate.Text = "" Then sqlCmdUpdate.Parameters("#JobDate").Value = DBNull.Value
If txtJobGrade.Text <> "" Then sqlCmdUpdate.Parameters("#JobGrade").Value = CInt(txtJobGrade.Text)
If txtJobGrade.Text = "" Then sqlCmdUpdate.Parameters("#JobGrade").Value = DBNull.Value
sqlCmdUpdate.ExecuteNonQuery()
Catch ex As Exception
lblErrMsg.Text = ex.ToString
lblErrMsg.Visible = True
Finally
sqlJobsDB.Close()
End Try
End Sub
Edit 2:
So I've pretty much given up on this, and instead moved the table into an FormView ItemTemplate, with an EditTemplate also. I modified it as described in the following link. http://www.beansoftware.com/ASP.NET-Tutorials/FormView-Control.aspx

Answer 1

Q1: Make sure the table structure allows nulls and set the parameter value to DBNull.Value.
Q2:
If IsNumeric(txtJobGrade.Text) Then
sqlCmdUpdate.Parameters("#JobGrade").Value = CInt(txtJobGrade.Text)
Else
sqlCmdUpdate.Parameters("#JobGrade").Value = 0 'Or Default Value
End If
You can always make that a drop down list to prevent open ended data input.

Answer 2

It's a little odd to see how you're done the parameters. Typically, I'd expect to see something more along these lines:
With sqlCmdUpdate.Parameters
.clear()
.addWithValue("#parm1", mytextbox1.text)
.addWithValue("#parm2", mytextbox2.text)
End With
For one, .add has been deprecated -- still works, but some issues to be aware of (http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlparametercollection.addwithvalue.aspx).
Secondly, it's always best to call .clear().
Also -- you might think about a more standard approach to checking for values -- for example:
If txtJobGrade.Text <> "" Then...
Would be better written as
If NOT string.isnullorempty(me.txtJobGrade.text) Then...
Try making a few of those changes, and see what (if any) errors you're still getting.