Search and remove "00:00" values from each column - excel

Question

I am trying to get my codes to go through each DateTime column and search for cells that contain "00:00" as hours and minutes. If the value exists, remove 00:00 and only leave the date. For the cells that don't contain that value, leave the cells as they are. For example, if "3/22/2017 00:00", then format it to "3/22/2017". Otherwise, if "3/22/2017 09:16", leave it alone. Thank you in advance!
dataGrid.DataSource = dataSet.Tables(0)
dataGrid.DataBind()
ws.Cells(1, 1).LoadFromDataTable(dataGrid.DataSource, True)
Dim data = dataGrid.DataSource
Dim columnCount = data.Columns.Count
For i = 0 To columnCount - 1
If data.Columns(i).DataType Is GetType(DateTime) Then
If Not data.Columns(i).ToString.Contains("00:00") Then
ws.Column(i + 1).Style.Numberformat.Format = "mm/dd/yyyy hh:mm"
Else
ws.Column(i + 1).Style.Numberformat.Format = "mm/dd/yyyy"
End If
End If
Next

Answer 1

For your solution to work, you would need to set the style on each individual cell. This is an inefficient solution as a style would be created for each cell. Is could be mitigated somewhat by defining two different styles and assigning those references to the cell as needed.
A simpler solution is use the DataGridView.CellFormatting Event to set the format when the cell is painted.
Evidently, the DateTime values have a time component less than one minute because the default formatting would have yield the desired result if this was not the case. The code below sets the format based on whether the time component is less than one minute.
Private Shared tsLimit As New TimeSpan(0, 1, 0) ' 1 minute
Private Shared dtType As Type = GetType(DateTime)
Private Sub dataGrid_CellFormatting(sender As Object, e As DataGridViewCellFormattingEventArgs) Handles dataGrid.CellFormatting
Dim dgv As DataGridView = CType(sender, DataGridView)
Dim dt As DataTable = TryCast(dgv.DataSource, DataTable)
If dt IsNot Nothing Then
Dim sourceColumn As DataColumn = dt.Columns.Item(dgv.Columns.Item(e.ColumnIndex).DataPropertyName)
If sourceColumn IsNot Nothing AndAlso sourceColumn.DataType Is dtType AndAlso e.Value IsNot Nothing AndAlso Not e.Value Is DBNull.Value Then
Dim d As DateTime = CDate(e.Value)
If d.TimeOfDay < tsLimit AndAlso d.Hour <> 0 Then
e.CellStyle.Format = "mm/dd/yyyy"
Else
e.CellStyle.Format = "mm/dd/yyyy hh:mm"
End If
End If
End If
End Sub

Answer 2

This can be accomplished by:
Setting a default format for all DateTime columns
Only overriding the default format for values that meet your criteria.
Here's a simple helper method that handles multiple DateTime columns:
Sub SetDateTimeStyles(ByRef data As DataTable, ByRef ws As ExcelWorksheet)
' Track DateTime columns to override default column style
Dim dateTimeColumns = New List(Of Integer)()
' Set column format
Dim columnCount = data.Columns.Count
For i = 0 To columnCount - 1
If data.Columns(i).DataType Is GetType(DateTime) Then
Dim epPlusColumn = i + 1
ws.Column(epPlusColumn).Style.Numberformat.Format = "mm/dd/yyyy hh:mm"
dateTimeColumns.Add(epPlusColumn)
End If
Next
' Header row exists; set to 1 if no header row
Dim rowOffset = 2
Dim rowCount = data.Rows.Count
' Only set cell format when hour and minute are **both** zero
For i = 0 To rowCount - 1
For Each dateTimeColumn In dateTimeColumns
Dim value As DateTime = data(i)(dateTimeColumn - 1)
If value.Hour = 0 AndAlso value.Minute = 0 AndAlso value.Second = 0 Then
ws.Cells(i + rowOffset, dateTimeColumn) _
.Style.Numberformat.Format = "mm/dd/yyyy"
End If
Next
Next
End Sub
And call it when creating the Excel file:
dataGrid.DataSource = dataSet.Tables(0)
dataGrid.DataBind()
ws.Cells(1, 1).LoadFromDataTable(dataGrid.DataSource, True)
Dim data As DataTable = dataGrid.DataSource
SetDateTimeStyles(data, ws)
Result: