I can't increase my table when I try to declare them that cause an error

Question

1.00/5 (1 vote)

See more:

Dim noofhalls As Integer
       Dim n As Integer
       Dim m As Integer
       Dim k As Integer
       Dim h As Integer
       Dim count As Integer

       noofhalls = Val(TextBox1.Text) / 15 'value is total number of strength and the values is 15
       If noofhalls > 1 Then
           For n = 1 To noofhalls - 1
               TabControl2.TabPages.Add("Hall" & n + 1)
           Next
       End If

       For n = 0 To noofhalls - 1
           dg = New DataGridView 'run-time datagridview is created
           dg.Size = New System.Drawing.Size(500, 500)
           dg.RowCount = 15
           dg.ColumnCount = 4
           dg.Columns(0).Name = "Seat No." 'first column labels
           dg.Columns(1).Name = "Reg, No." 'second column labels
           dg.Columns(2).Name = "Seat No." 'third column labels
           dg.Columns(3).Name = "Reg, No." 'fourth column labels

           For k = 0 To 14
               dg.Rows(k).Cells(0).Value = k + 1 'defining the seat
           Next
           h = 0

           For k = 16 To 100
               dg.Rows(h).Cells(2).Value = k + 1
               h += 1
           Next

           TabControl2.TabPages(n).Controls.Add(dg)

       Next
       count = 0
       Dim x, y As Integer
       For Each Str1 In ListBox2.Items
           Dim sql1 As String = "select count(regd_no) from class_table where class ='" + Str1 + "'"
           Dim sql As String = "select regd_no from class_table where class ='" + Str1 + "'"
           cmd1 = New SqlCommand(sql, conn)
           cmd = New SqlCommand(sql1, conn)
           count = Convert.ToInt16(cmd.ExecuteScalar)
           dr = cmd1.ExecuteReader()
           x = 1
           y = 1
           If count <= 100 Then
               While dr.Read And x <= 100

                   If x <= 1 Then
                       dg.Rows(x - 1).Cells(1).Value = dr(0).ToString
                       x += 2
                   End If
                   If x > 15 Then
                       dg.Rows(y - 1).Cells(3).Value = dr(0).ToString
                       y += 2
                   End If

               End While


           End If
           dr.Close()
       Next

   End Sub

What I have tried:

This is a Exam Hall Arrangement Project and I already set only 15 Students in my code.then, I try to increase them to some 'n' Value and it Show the error and I am trying to rectify them but i cannot solve codes...can anyone help me with this..

Posted 28-Apr-20 5:44am

Nithish685

Updated 28-Apr-20 6:29am

Add a Solution

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

MadMyche · Accepted Answer · 2020-04-28T06:30:00

For starters you have a multitude of problems in your SQL block
Line 1 is vulnerable to SQL Injection.
Line 2 is also vulnerable
Line 3 is not needed and increases memory usage
Line 5 has a syntax error- should be count = Convert.ToInt16(cmd.ExecuteScalar())

VB

Dim sql1 As String = "select count(regd_no) from class_table where class ='" + Str1 + "'"
Dim sql As String = "select regd_no from class_table where class ='" + Str1 + "'"
cmd1 = New SqlCommand(sql, conn)
cmd = New SqlCommand(sql1, conn)
count = Convert.ToInt16(cmd.ExecuteScalar)
dr = cmd1.ExecuteReader()

NEVER EVER build an SQL query by concatenating commands with variables

This is how I would write this; using Parameters to get rid of the vulnerability, fix the syntax error, and reuse the cmd object by simply changing the CommandText and keeping the existing parameter

VB

Dim sql1 As String = "SELECT count(regd_no) FROM class_table WHERE class = @Str1"
Dim sql As String = "SELECT regd_no FROM class_table WHERE class = @Str1"

' cmd1 = New SqlCommand(sql, conn)

cmd = New SqlCommand(sql1, conn)
cmd.Parameters.AddWithValue("@Str1", Str1)

count = Convert.ToInt16(cmd.ExecuteScalar())

cmd.CommandText = sql
dr = cmd.ExecuteReader()