How to enable a button if regex expression is valid - asp.net

Question

I have a page on which there are two textboxes that have a regular expression on them.
ASPX Code TextBox 1
<asp:TextBox ID="txtCasesInsert" runat="server" Width="50px"></asp:TextBox>
<asp:RequiredFieldValidator ID="rfvCases" ControlToValidate="txtCasesInsert" ValidationGroup="InsertRecord"
runat="server" ErrorMessage="*" ForeColor="Red"></asp:RequiredFieldValidator>
<asp:RegularExpressionValidator ID="regexCases" ControlToValidate="txtCasesInsert"
ValidationExpression="[0-9]+(,[0-9]+)*" ForeColor="Red" ErrorMessage="Please seperate numbers with a comma"
runat="server" />
ASPX Code TextBox 2
<asp:TextBox ID="txtPremiumInsert" runat="server" Width="50px"></asp:TextBox>
<asp:RequiredFieldValidator ID="rfvPremium" ControlToValidate="txtPremiumInsert"
ValidationGroup="InsertRecord" runat="server" ErrorMessage="*" ForeColor="Red"></asp:RequiredFieldValidator>
<asp:RegularExpressionValidator ID="regexPremium" ControlToValidate="txtPremiumInsert"
ValidationExpression="[0-9]+(,[0-9]+)*" ForeColor="Red" ErrorMessage="Please seperate numbers with a comma"
runat="server" />
The regular expression works as intended for both text boxes.
What I need now is to be able to check the text being inputted into those text boxes and if the regular expression is valid, then enable my Insert button, otherwise, keep the button disabled.
Insert Button
<asp:Button ID="btnInsertRecord" Width="100px" Height="25px" runat="server" Text="Add Record"
CssClass="buttonBlue" ValidationGroup="InsertRecord" />
The reason I want to do this, is because when the regex has an error, the page still allows the user to insert data so I thought of disabling the button if the regex isn't successfull to prevent this.
I tried this C# If regex doesn't match then do something and I've also read up on Microsofts Regex documentation to learn more about what I can do with Regex's but I haven't found any information related to what I need.
I also tried creating a function with a TextChanged method hooked onto the textboxes but it didn't work. No error messages, just the button wasn't disabling when I inputted a wrong string. That's the problem I'm also having now with my current code. It's like nothing is happening. I've hooked the debugger on the _premiumMatch.Success line but again, nothing is happening, it just lets me proceed. When I created the TextChanged method for my button, I also tried adding it into my Page Load method but that disabled the button straight away.
Current VB Code (Example with one of the text boxes)
Dim _regex As Regex = New Regex("[0-9]+(,[0-9]+)*")
Dim _premiumMatch = _regex.Match(txtPremiumInsert.Text)
If _premiumMatch.Success Then
Try
Company.Applications.ProductionEngine.BusinessAccess.ExcelFileContentUploadBusinessAccess.InsertLimitInsurance(_branch,
_premium,
_cases,
_ddlMonths,
_ddlYear)
Catch ex As Exception
InformationBox.ShowErrorMessage("Record not added. Please try again")
End Try
loadLimitInsurances()
InformationBox.ShowSuccessMessage("New Record Inserted")
txtBranchInsert.Text = ""
txtPremiumInsert.Text = ""
txtCasesInsert.Text = ""
End If
Not sure what I'm doing wrong. Any suggestions? The above VB code, for now is in my buttons click event but even with an invalid regex, when I click the insert is still performed.
First Edit
Just tried calling the below function in my page load but the button disables straight away and does not become enabled if I input a valid regex. Again, example is for one textbox.
Protected Friend Sub CheckPremium() Handles txtPremiumInsert.TextChanged
Dim _regex As Regex = New Regex("[0-9]+(,[0-9]+)*")
Dim _match As Match = _regex.Match(txtPremiumInsert.Text)
If _match.Success Then
btnInsertRecord.Enabled = True
Else
btnInsertRecord.Enabled = False
End If
End Sub
Second Edit
I have tried the above code and I've activated AutoPostBack on the textbox and still when I type an invalid expression it postbacks and activates my button.

Answer 1

Try this code:
Dim _regex As Regex = New Regex("[0-9]+(,[0-9]+)*")
Dim FoundMatch As Boolean = _regex.IsMatch(textPremiumInsert.Text)
If FoundMatch = True Then
Try
Company.Applications.ProductionEngine.BusinessAccess.ExcelFileContentUploadBusinessAccess.InsertLimitInsurance(_branch,
_premium,
_cases,
_ddlMonths,
_ddlYear)
Catch ex As Exception
InformationBox.ShowErrorMessage("Record not added. Please try again")
End Try
loadLimitInsurances()
InformationBox.ShowSuccessMessage("New Record Inserted")
txtBranchInsert.Text = ""
txtPremiumInsert.Text = ""
txtCasesInsert.Text = ""
End If
The code above uses the Regex.IsMatch method to compare the string passed with the regex pattern. It returns true if the string matches the Regex pattern.