String was not recognized as a valid DateTime.

Question

I am retrieving data into gridview ,using template field and selecting data from gridview using event of selectedindex changed,

i have column of date,in which null value also have,

                     <asp:TemplateField HeaderText="Approve_Date" >
                                <ItemTemplate>
                                    <asp:Label ID="App_Date" runat="server" Text='<%#Eval("App_Date")%>'></asp:Label>
                                </ItemTemplate>
             </asp:TemplateField>

when i selecting row using below code

    txtappdate.Text = Convert.ToDateTime((GVballist.SelectedRow.FindControl("App_Date") as Label).Text).ToString("yyyy-MM-d").Replace(" ", null);

then it is giving error String was not recognized as a valid DateTime.
txtappdate.text Text Mode is date.

Answer 1

Ok, the way this works is a bit confusing.

If you use auto generated column, OR YOU use databound fields, eg like this:

                    <asp:BoundField DataField="BookingDate"   HeaderText="Book Date"   />

Then of course you do NOT use FindControl, but in fact use the .Cells[] colleciton.

ONLY WHEN you use .Cells[] collection does the text value for a null return that " "

But, WHEN you use a textbox, label etc.? (and FindControl)?

Then a null does return a empty string.

eg this:

       protected void GridView1_SelectedIndexChanged(object sender, EventArgs e)
        {
            string str = ((Label)GridView1.SelectedRow.FindControl("txtBDate")).Text;

            if (str == "")
            {
                TextBox1.Text = "blank value";
            }
            else
            {
                //TextBox1.Text = str;
                TextBox1.Text = Convert.ToDateTime(str).ToString("yyyy-MM-dd");
            }

        }

So in fact, since you ARE using a templated field, then you test for "" for nulls. But you are correct that when the grid renders, asp.net DOES CONVERT nulls to that " " since some browsers will not render a table correct without a blank in that cell.

So:

For cells[], and a null? (yes nulls convert to HTML space). And YES you do test for that HTML space like (some value == " ".

For templated controls such as label, text box? The null value is a empty string.

So, test for "" and you should be fine. And yes, it is VERY easy to mess this up, since you might have some code, databound fields - they DO return that HTML blank space, but templated controls do not use the cells[] collection, and they don't return HTML spaces, but an real empty string for null values.

Regards, Albert D. Kallal (Access MVP 2003-2017) Edmonton, Alberta Canada

Answer 2

Hi @Analyst_SQL ,
According to your problems,I reproduced it. First,you need to make sure if the Label of App_Date isn't null. It may cause your problem.And then you could use ParseExact() to parse the data.
123903-new-text-document-3.txt
Best regards,
Yijing Sun

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