vb.net - How can I change the type of values that the DataTable can store? - vb.net

Question

I want to add characters (like % and pp) in values stored in a DataTable, but I'm getting an error message:
Input string was not in a correct format.Couldn't store <97.0%> in Actual Column. Expected type is Decimal.
How can I change the type of values that the DataTable can store?
Dim dv As New System.Data.DataView
Dim dt As New System.Data.DataTable
dv = SQL_Customer.Select(DataSourceSelectArguments.Empty)
dt = dv.ToTable()
dt.Rows(1)(1) = CStr(dt.Rows(1)(1)) & "%"
dt.Rows(1)(2) = CStr(dt.Rows(1)(2)) & "%"
dt.Rows(1)(3) = CStr(dt.Rows(1)(3)) & "%"
dt.Rows(1)(4) = CStr(dt.Rows(1)(4)) & "pp"

Answer 1

You can't change the type of a data table column once it's filled.
One work around is to add a new column of type string and then populate that column with the string values you need and then delete the column that is of the type you don't need.

Answer 2

If this helps someone, this is how I resolved the problem:
Dim dv As New System.Data.DataView
Dim dt As New System.Data.DataTable
Dim dt2 As New System.Data.DataTable
Dim SelectedIndex As Object
If datagrid.SelectedIndex = "-1" Then SelectedIndex = 0 Else SelectedIndex = GV_Cust.SelectedIndex
'Populate Dataview with data in SQL Query for Customer KPIs
dv = SQL_Customer.Select(DataSourceSelectArguments.Empty)
'Populate table with data from dataview. Note that the data is formated as per data loaded. So if number is loaded, then format for the cell is number. This creates a problem when adding percentages
dt = dv.ToTable()
'New colums are added as string format in the dataTable so that % and pp can be added
Dim column As DataColumn
For i = 1 To 6
' Create second column.
column = New DataColumn()
column.DataType = System.Type.GetType("System.String")
column.ColumnName = i
column.AutoIncrement = False
column.Caption = i
column.ReadOnly = False
column.Unique = False
' Add the Column to the DataColumnCollection.
dt.Columns.Add(column)
Next
'New columns are populated and calculations for variances are calculated
For j = 0 To 2
For i = 0 To 4
dt.Rows(i)(7 + j) = dt.Rows(i)(1 + j) & "%"
dt.Rows(i)(10) = (dt.Rows(i)(1) - dt.Rows(i)(2)) & "pp"
dt.Rows(i)(11) = (dt.Rows(i)(1) - dt.Rows(i)(3)) & "pp"
dt.Rows(i)(12) = (dt.Rows(i)(2) - dt.Rows(i)(3)) & "pp"
Next
For i = 5 To 6
dt.Rows(i)(7 + j) = dt.Rows(i)(1 + j)
If dt.Rows(i)(2) = 0 Then dt.Rows(i)(10) = 0 & "%" Else dt.Rows(i)(10) = Math.Round((((dt.Rows(i)(1) / dt.Rows(i)(2))) - 1) * 100, 1) & "%"
If dt.Rows(i)(3) = 0 Then dt.Rows(i)(11) = 0 & "%" Else dt.Rows(i)(11) = Math.Round((((dt.Rows(i)(1) / dt.Rows(i)(3))) - 1) * 100, 1) & "%"
If dt.Rows(i)(3) = 0 Then dt.Rows(i)(12) = 0 & "%" Else dt.Rows(i)(12) = Math.Round((((dt.Rows(i)(2) / dt.Rows(i)(2))) - 1) * 100, 1) & "%"
Next
Next
'Old columns are deleted and new wones are renamed
dt.Columns.Remove("A")
dt.Columns("1").ColumnName = "A"
dt.Columns.Remove("B")
dt.Columns("2").ColumnName = "B
dt.Columns.Remove("C")
dt.Columns("3").ColumnName = "C"
dt.Columns.Remove("D")
dt.Columns("4").ColumnName = "D"
dt.Columns.Remove("D")
dt.Columns("5").ColumnName = "E"
dt.Columns.Remove("F")
dt.Columns("6").ColumnName = "F"
'Customer grid is populated, a selection button is added and the first row is selected
datagrid.DataSource = dt
datagrid.AutoGenerateSelectButton = True
datagrid.DataBind()
datagrid.SelectedIndex = SelectedIndex