CODEWITHSUNDEEP
vb.netwinformsdatatable
Pranav1688
Pranav1688

Reputation: 175

DataTable Column.Expression Throw Error

I Have Data Table which Contains Few row like below 

CH1 CH2 Ch3 CH4 CH5
1   2   1   2   3
3   3   1   2   3
3   3   1   1   2
1   3   3   3   3
1   2   3   3   0
3   3   1   2   0
3   3   1   1   2

then I Try to add new column like

Dim col As New DataColumn("VCH1", GetType(Decimal),"(CH1+CH2+ch3)/CH5")
DtReadings.Columns.Add(col)

at that time give me error : Attempted to divide by zero. Because of CH5 have zero values, but I need to add Dynamic Column with different Expression at run time ,how to avoid such type of error any Idea please Help.

Expression value not fixed,User Create expression for dynamic Column. not only handle divide by zero error ,to handle all type of computing error

Upvotes: 1

Views: 1811

Answers (3)

Pranav1688
Pranav1688

Reputation: 175

Simply Create One Extension for Solve my Problem,that's take a time but i have no problem

<Extension()>
Public Function ToCompute(value As DataTable, exp As String, inputColumn As String) As DataTable
    Dim tempdt As New DataTable
    tempdt = value.Clone
    tempdt.Columns(inputColumn).Expression = exp
    For Each row As DataRow In value.Rows.Cast(Of DataRow).ToList
        Try
            tempdt.Rows.Add(row.ItemArray)
            value.Rows(value.Rows.IndexOf(row))(inputColumn) = tempdt.Rows(0)(inputColumn).ToString
            tempdt.Rows.Clear()
        Catch ex As Exception
            tempdt.Rows.Clear()
            value.Rows(value.Rows.IndexOf(row))(inputColumn) = 0
            Continue For
        End Try
    Next
    Return value
End Function

Upvotes: 0

Steve
Steve

Reputation: 216273

The Expression syntax allow the use of the IIF statement
You could build your DataColumn using this kind of syntax for the Expression

col = New DataColumn("VCH1", GetType(Decimal), "IIF(CH5 = 0, 0, (CH1+CH2+ch3)/CH5)")

Of course, being the Expression a string property you could build your expression dynamically based on the particular requirement you have at the moment. With IIF or ISNULL you could build your string on the fly before adding the column. Something like this pseudocode

Dim currentExpression as String = BuildCurrentExpression() 
col = New DataColumn("VCH1", GetType(Decimal), currentExpression)

Upvotes: 1

SysDragon
SysDragon

Reputation: 9888

You can catch the DivideByZeroException and then assign the value you want:

Try
    col = New DataColumn("VCH1", GetType(Decimal), "(CH1+CH2+ch3)/CH5")
Catch ex As DivideByZeroException
    col = New DataColumn("VCH1", GetType(Decimal), "0")
End Try

DtReadings.Columns.Add(col)

Upvotes: 1

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