如何将DateTime转换为字符串

Question

The ra.Value in the while loop sometimes is DateTime type and unfortunately the .ToString() method is not enough to convert it to string. What I should change on my code, to recognize when ra.Value is DateTime type and convert it to String. Now I have the exception that conversion from type 'DateTime' to type 'String' is not valid.

With ro.Attributes.GetEnumerator
    While .MoveNext
        Dim ra As ReportAttribute = CType(.Current, ReportAttribute)
        Dim lstrColumnReportObj As Integer = ra.Column
        Dim lstrValueReportObj As String = ra.Value.ToString()
        lstrParTable(lstrColumnReportObj) = lstrParTable(lstrColumnReportObj) + lstrValueReportObj
    End While
End With

Thank you.

Answer 1

The simple solution that you are probably looking for is this:

With ro.Attributes.GetEnumerator
    While .MoveNext
        Dim ra As ReportAttribute = CType(.Current, ReportAttribute)
        Dim lstrColumnReportObj As Integer = ra.Column
        Dim lstrValueReportObj As String = Nothing
        If TypeOf ra.Value Is Date Then
            lstrValueReportObj = ra.Value.ToString("d MMM yyyy")
        Else
            lstrValueReportObj = ra.Value.ToString()
        End If
        lstrParTable(lstrColumnReportObj) = lstrParTable(lstrColumnReportObj) + lstrValueReportObj
    End While
End With

However, this does smack of bad practice and you may want to reconsider your overall design. Usually, when you have to start putting in special logic for certain types, like that, it's usually a sign that you could be doing it in a better way. For instance, what will happen when you start needing custom formatting for other types as well. Once you have more than a handful of exceptions, it's going to get unwieldy and the code will be brittle (prone to bugs).

Also, I feel obligated to mention that hungarian notation is discouraged in .NET. If you are required to use it by your employer, that's fine, but otherwise, I'd recommend reading through the official Microsoft naming guidelines .