Must declare the scalar variable "#??????" - sql-server

Question

I am using the following SQL statement :
Dim strSql5 As String = "SELECT * FROM dbo.ontledings " & _
" where plaasblok = #plaasblokparsversoeke " & _
" and analisedatum = #laastedatum"
cnn.Open()
Dim aksie2 As New SqlClient.SqlCommand(strSql5, cnn)
aksie2.Parameters.Add("#plaasblokparsversoeke", SqlDbType.VarChar).Value = plaasblokparsversoeke
aksie2.Parameters.Add("#laastedatum", SqlDbType.Date).Value = laastedatum
aksie2.ExecuteNonQuery()
cnn.Close()
I want to fill a datatable like so :
Dim dtb5 As New DataTable
dtb5.Clear()
Using cnn As New SqlConnection("Data Source=GIDEON-E-LAPTOP\SQLEXPRESS2014;Initial Catalog=SkeduleringDatabasis;Integrated Security=True")
cnn.Open()
Using dad5 As New SqlDataAdapter(strSql5, cnn)
dad5.Fill(dtb5)
End Using
cnn.Close()
End Using
I get the following error message : Must declare the scalar variable "#plaasblokparsversoeke"
I cannot figure out where and how to declare the scalar variables.
The error occurs at the line : dad5.Fill(dtb5)
Regards

Answer 1

You need to add the parameters like
cmd.Parameters.Clear()
cmd.Parameters.AddWithValue("#plaasblokparsversoeke", plaasblokparsversoeke.Text)
cmd.Parameters.AddWithValue("#laastedatum", laastedatum.Text)
As correctly commented below, you need to use the Add method to add the paramters:
cmd.Parameters.Add("#plaasblokparsversoeke", SqlDbType.Varchar).Value = plaasblokparsversoekeVariable;
cmd.Parameters.Add("#laastedatum", SqlDbType.Varchar).Value = laastedatumVariable;

Answer 2

Firstly, avoid hard-coding a parameterised query in this way, for avoidance of SQL injection.
To answer your specific question: you are trying to use parameters in the query without having defined them in the SQLCommand.
Have a look at MSDN for the full documentation.

Answer 3

With this query
Dim strSql5 As String = "SELECT * FROM dbo.ontledings " & _
" where plaasblok = #plaasblokparsversoeke " & _
" and analisedatum = #laastedatum"
You are definining 2 SQL variables called #plaasblokparsversoeke and #laastedatum that you have to pass as parameters to your command, like this
command.Parameters.Add("#plaasblokparsversoeke", SqlDbType.Int);
command.Parameters["#plaasblokparsversoeke "].Value = yourValue;
MSDN article on SQL command parameters here