Problem on finding the max and min value

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My code for minimum values return the maximum value and the code for maximum returns 0

VB

Private Sub BtnCalcMin_Click(sender As Object, e As EventArgs) Handles btnCalcMin.Click
        'Minimum Calculation 

        Dim strsql As String = "SELECT [Price] FROM [Booking]"
        Dim strpath As String = "Provider=Microsoft.JET.OLEDB.4.0;Data Source=C:\Users\User\Desktop\Dummy database for login register\Flight2\Flight\test.mdb"

        Dim odaTest As New OleDb.OleDbDataAdapter(strsql, strpath)
        Dim datvalue As New DataTable

        Dim intcount As Integer

        Dim decMinimum As Decimal = 0

        odaTest.Fill(datvalue)
        odaTest.Dispose()


        For intcount = 0 To datvalue.Rows.Count - 1
            If decMinimum >= Convert.ToDecimal(datvalue.Rows(intcount)("Price")) Then
                decMinimum = Convert.ToDecimal(datvalue.Rows(intcount)("Price"))
            Else
                decMinimum = decMinimum
            End If
        Next

        Label5.Text = "RM" & decMinimum

    End Sub

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
       'Maximum Calculation 

        Dim strsql As String = "SELECT [Price] FROM [Booking]"
        Dim strpath As String = "Provider=Microsoft.JET.OLEDB.4.0;Data Source=C:\Users\User\Desktop\Dummy database for login register\Flight2\Flight\test.mdb"

        Dim odaTest As New OleDb.OleDbDataAdapter(strsql, strpath)
        Dim datvalue As New DataTable

        Dim intcount As Integer

        Dim decMax As Decimal = 0

        odaTest.Fill(datvalue)
        odaTest.Dispose()

        For intcount = 0 To datvalue.Rows.Count - 1
            If decMax < Convert.ToDecimal(datvalue.Rows(intcount)("Price")) Then
                decMax = Convert.ToDecimal(datvalue.Rows(intcount)("Price"))
            End If
        Next

        Label6.Text = "RM" & decMax
    End Sub

What I have tried:

I tried changing the data type from currency to numbers

Posted 15-Dec-19 5:35am

Wafiqque

Updated 15-Dec-19 6:08am

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Comments

phil.o 15-Dec-19 11:56am

This is a mathematical issue: you do not use the right comparisons for maximum/minimum values. This is the kind of problem which can be understood/solved by a simple debug session. Why don't you debug your code?

3 solutions

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Patrice T · Answer 1 · 2019-12-15T05:53:00

Quote:
My code for minimum values return the maximum value and the code for maximum returns 0

For Mon and Max, never start with a fixed value like 0, always start with an element of the list, usually the first.
-----
Your code do not behave the way you expect, or you don't understand why !

There is an almost universal solution: Run your code on debugger step by step, inspect variables.
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't know what your code is supposed to do, it don't find bugs, it just help you to by showing you what is going on. When the code don't do what is expected, you are close to a bug.
To see what your code is doing: Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.

Debugger - Wikipedia, the free encyclopedia[^]

Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]

Visual Basic / Visual Studio Video Tutorial - Basic Debugging - YouTube[^]
Visual Basic .NET programming for Beginners - Breakpoints and Debugging Tools[^]

The debugger is here to only show you what your code is doing and your task is to compare with what it should do.

Maciej Los · Answer 2 · 2019-12-15T05:40:00

Solution 1

On SQL Server level:

SQL

SELECT DISTINCT MIN([Price]), MAX([Price]) FROM [Booking]

On client level

VB

Dim minval = datvalue.AsEnumerable().Min(Function(x) x.Field(of Integer)("Price"))
Dim maxval = datvalue.AsEnumerable().Max(Function(x) x.Field(of Integer)("Price"))

Posted 15-Dec-19 5:40am

Maciej Los

Comments

Wafiqque 15-Dec-19 11:43am

it says sequence contains no element

Richard MacCutchan · Answer 3 · 2019-12-15T06:08:00

The variable decMinimum starts at zero, so it will never be replaced by any other value. The decMaximum also starts at zero, but we must assume there are no values in the datatable otherwise it would be replaced. As Patrice T suggests, use the debugger to see what actual values (if any) you are processing. Also remove that redundant Else clause in your code:

VB

If decMinimum >= Convert.ToDecimal(datvalue.Rows(intcount)("Price")) Then
    decMinimum = Convert.ToDecimal(datvalue.Rows(intcount)("Price"))
' Else                         these lines are redundant
'    decMinimum = decMinimum           ditto
End If

Problem on finding the max and min value

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Problem on finding the max and min value

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