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Thread: Datagridview Error

  1. #1

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    Datagridview Error

    In my datagridview I have 3 columns, lets say Column1, 2, 3.

    Column1 is Column2 / Column3.

    Problem I have is I'm trying to prevent an error if the user types "0" into Column 2 or 3. I can prevent against it dividing by null or a letter by the following codes:

    Code:
    If Not IsNull(Me.DataDataGridView1.CurrentRow.Cells("Column2").Value) Then
    and
    Code:
    If IsNumeric(Me.DataDataGridView1.CurrentRow.Cells("FieldName").Value) Then
    But, I can't protect it from someone typing "0" because zero is numeric and
    Code:
    If Me.DataDataGridView1.CurrentRow.Cells("FieldName").Value = 0 Then
    causes problems as well because it treats 0 as null.

    Any ideas are appreciated.

  2. #2
    PowerPoster make me rain's Avatar
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    Wink Re: Datagridview Error

    i don't think you need to handle this issue this way

    i would like to say
    (1) you cross check numeric values
    (2) you cross check null entries, i mean ""

    then come to division part.

    it is up to you which column value should be more & which should be less
    but still if the value is 0 then handle it with in the function which returns the column 1 cell value accordingly .. check this function.
    vb.net Code:
    1. Private Function JpiPer() As Double
    2.         Dim Col_2value As Double = 10
    3.         Dim Col_3value As Double = 0
    4.         Dim outPut As Double
    5.  
    6.  
    7.         If Double.IsInfinity(Col_2value / Col_3value) Then
    8.             outPut = 0
    9.         Else
    10.             outPut = Col_2value / Col_3value
    11.         End If
    12.  
    13.         MessageBox.Show(outPut)
    14.  
    15.         Return outPut
    16.     End Function
    The averted nuclear war
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    PrOtect your PC. MSDN Functions .OOP LINUX forum
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  3. #3

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    Re: Datagridview Error

    This works fine if I'm using existing data, but when I add a row it gives me a dbnull crash. Also I can get it to update the text in the message box to what it should say but I cannot get the value displayed in the message box to display in Column 1.


    All I'm looking for is the the following:

    Column1 = Column2 / Column3

    BUT.....

    My main goal is to allow the user to leave Columns 2 and 3 Null, type letters, do anything you want to do, and it only calculates Column 1 if Column 2 and 3 contain numbers (greater than 0).

    Thanks

  4. #4
    PowerPoster make me rain's Avatar
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    Re: Datagridview Error

    Code:
    but when I add a row
    (1) how u are adding the row & then performing what action fallow correct sequence
    Code:
    All I'm looking for is the the following:
    Column1 = Column2 / Column3
    (2) that is what the above function is doing
    Code:
    allow the user to leave Columns 2 and 3 Null, type letters,
    if so manipulate it in your code as if , column values are irrelevant then replace it with 0

    the best solution is show your code
    The averted nuclear war
    My notes:

    PrOtect your PC. MSDN Functions .OOP LINUX forum
    .LINQ LINQ videous
    If some one helps you please rate them with out fail , forum doesn't expects any thing other than this

  5. #5
    Karen Payne MVP kareninstructor's Avatar
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    Re: Datagridview Error

    You can handle dealing with not allowing zero in CellValidating event of the DataGridView.

    Example, we have a column named DepartmentNumberColumn which only numerics are allows and on edit or add we have a default value of 100 we can do the following
    Code:
        Sub DataGridView1_CellValidating( _
            ByVal sender As Object, _
            ByVal e As System.Windows.Forms.DataGridViewCellValidatingEventArgs) _
            Handles DataGridView1.CellValidating
    
            Dim GridView As DataGridView = DataGridView1
    
            Dim cell As DataGridViewCell = GridView.Item(e.ColumnIndex, e.RowIndex)
    
            If cell.IsInEditMode Then
                Dim c As Control = GridView.EditingControl
    
                Select Case GridView.Columns(e.ColumnIndex).Name
                    Case "DepartmentNumberColumn"
                        c.Text = NumberCleaner(c.Text)
                End Select
            End If
    
        End Sub
    
        Function NumberCleaner(ByVal str As String) As String
            Dim Value As String = System.Text.RegularExpressions.Regex.Replace(str, "[a-zA-Z\b\s-.]", "")
            If Value.Length > 0 Then
                If Value = "0" Then
                    Value = "100"
                End If
            Else
                Value = "100"
            End If
            Return Value
        End Function
    Then for new rows suggest default values
    Code:
        Private Sub DataGridView1_DefaultValuesNeeded( _
            ByVal sender As Object, _
            ByVal e As System.Windows.Forms.DataGridViewRowEventArgs) _
            Handles DataGridView1.DefaultValuesNeeded
    
            e.Row.Cells("DepartmentNameColumn").Value = "English"
            e.Row.Cells("DepartmentNumberColumn").Value = 100
        End Sub
    If you want to indicate to the user the problem then look at setting the cell's ErrorText when there is an issue and then when the issue is resolved remove the ErrorText.

  6. #6

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    Re: Datagridview Error

    Thanks Kevin, I'm with you here, just would appreciate it if you could try to picture my project and maybe give me a some additional pointers for validating.

    I'm building a grid for users to add rows for new tests, probably 4 to 8 tests(rows) combined on each sample(form with sample info). When you add a new sample(refresh form) the grid will start over blank from a new databound relationship row added. My original plan was to have each sample start with an empty grid with 9 columns. Col1 is an ID, it will have default value. Col2 is an "age" column, the user enters how many days from the "sample date" the test is to occur. Col3 is a calculated date of user entered textbox date + Col2 (you helped me with this one). Col4 user enters a diameter. Col5 is an area calculation based off diameter entered in Col4. Col6 is pounds of force that the user enters. Col7 is calculation of PSI which is Col6 divided by Col5. Col8 is default "Specified PSI". Col9 is Percent of PSI which is Col7 / Col8.

    Basically you can see how nulls and zeros and letters can cause a major problem for me, especially when creating the next rows by arrowing down and when dividing by other calculated columns. I have it all coded so the math's good. What I need help with is making an error proof grid that will take whatever the user throws at it. Preferably I'd like the grid to only calculate if there is a number in the applicable text boxes, otherwise it ignores the calculation and you can type anything in a cell - letters, zeros, leave it blank, it don't matter. I tried message boxes and it is a pain because they pop up when you make a new row and I just think they are annoying. I can get it to work most of the time using ISDBNULL or ISNUMERIC but some zeros still slip through and saying =0 or <1 is like saying "null" which will make it fire when a new row is added.

    I know, it sounds more like an excel spreadsheet than a database. Not really a wise idea for my first ever program but hey, swing for the fences right Thanks for helping guys.

  7. #7
    Karen Payne MVP kareninstructor's Avatar
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    Re: Datagridview Error

    Quote Originally Posted by jpiper View Post
    Thanks Kevin, I'm with you here, just would appreciate it if you could try to picture my project and maybe give me a some additional pointers for validating.

    I'm building a grid for users to add rows for new tests, probably 4 to 8 tests(rows) combined on each sample(form with sample info). When you add a new sample(refresh form) the grid will start over blank from a new databound relationship row added. My original plan was to have each sample start with an empty grid with 9 columns. Col1 is an ID, it will have default value. Col2 is an "age" column, the user enters how many days from the "sample date" the test is to occur. Col3 is a calculated date of user entered textbox date + Col2 (you helped me with this one). Col4 user enters a diameter. Col5 is an area calculation based off diameter entered in Col4. Col6 is pounds of force that the user enters. Col7 is calculation of PSI which is Col6 divided by Col5. Col8 is default "Specified PSI". Col9 is Percent of PSI which is Col7 / Col8.

    Basically you can see how nulls and zeros and letters can cause a major problem for me, especially when creating the next rows by arrowing down and when dividing by other calculated columns. I have it all coded so the math's good. What I need help with is making an error proof grid that will take whatever the user throws at it. Preferably I'd like the grid to only calculate if there is a number in the applicable text boxes, otherwise it ignores the calculation and you can type anything in a cell - letters, zeros, leave it blank, it don't matter. I tried message boxes and it is a pain because they pop up when you make a new row and I just think they are annoying. I can get it to work most of the time using ISDBNULL or ISNUMERIC but some zeros still slip through and saying =0 or <1 is like saying "null" which will make it fire when a new row is added.

    I know, it sounds more like an excel spreadsheet than a database. Not really a wise idea for my first ever program but hey, swing for the fences right Thanks for helping guys.
    Unfortunately adding and editing within a DataGridView is possible in short as you have learned already things get messy fast. This is why I only allow add/edit by showing a modal dialog for these purposes where it is simpler to manage these operations. My thought is just because you can add and edit in a DataGridView does not mean you should without understanding how to implement and how to maintain code later.

    What I would suggest is if the user is entering many records at once to use a modal dialog, they press save, validation is done then save the data to a BindingSource which is the DataSource of the DataGridView. The modal dialog only closes when the user presses the dialog’s close button.

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