如何将日期格式从MM / dd / yyyy更改为dd-MM-yyyy？

Question

I want to add the days in current date i have created the code but it showing error String was not recognized as a valid DateTime. I want the date format like this 'dd-MM-yyyy'

Here is my Script

<script>
        function addDate() {
            debugger;
            //Get the entered datevalue
            var enteredDateVal = new moment(document.getElementById("TextBoxStartDate").value);
            //Get the days to add 
            var numberofDays = document.getElementById("TextBoxPredictDays").value
            //Add the days using add method in moment.js
            enteredDateVal.add("days", parseInt(numberofDays));
            //Assign the value in textbox
            document.getElementById("TextBoxPredictedClosing").value = enteredDateVal.format("dd-MM-yyyy");
        }
    </script>

and here is my Code Behind for Button Click

protected void Button9_Click(object sender, EventArgs e)
    {
       // this.TextBoxStartDate ="dd-MM-yyyy";
        DateTime dtval = DateTime.Parse(TextBoxStartDate.Text);
        //Add values here
        DateTime formatteddays = dtval.AddDays(Int16.Parse(TextBoxPredictDays.Text));
        TextBoxPredictedClosing.Text = formatteddays.ToString("dd-MM-yyyy");
    }

I am updating with error for All of you dear and thanks for response kindly help here is the Error

Answer 1

Use DateTime.ParseExact() to get date object from string as

protected void Button9_Click(object sender, EventArgs e)
    {
       // this.TextBoxStartDate ="dd-MM-yyyy";
        DateTime dtval = DateTime.ParseExact(TextBoxStartDate.Text, "dd-MM-yyyy", System.Globalization.CultureInfo.InvariantCulture, System.Globalization.DateTimeStyles.None);
        //Add values here
        DateTime formatteddays = dtval.AddDays(Int16.Parse(TextBoxPredictDays.Text));
        TextBoxPredictedClosing.Text = formatteddays.ToString("dd-MM-yyyy");
    }

You can also check string for valid date as

public static bool IsDate(string tempDate)
        {        
            DateTime fromDateValue;
            var formats = new[] { "dd-MM-yyyy" };
            if (DateTime.TryParseExact(tempDate, formats, System.Globalization.CultureInfo.InvariantCulture, System.Globalization.DateTimeStyles.None, out fromDateValue))
            {
                return true;
            }
            else
            {
                return false;
            }
        }

You can refer to link for Date check http://www.niceonecode.com/QA/DotNet/CSharp/how-to-check-valid-date-in-c/20271

Answer 2

Your code seems to be right but your TextBoxStartDate is not in the correct format.

Try using

DateTime myDate = DateTime.ParseExact(TextBoxStartDate.Text, "dd-MM-yyyy",
         System.Globalization.CultureInfo.InvariantCulture);
int numVal = Int32.Parse(TextBoxPredictDays.Text);
myDate.AddDays(numVal);

And make sure that your input format (dd-MM-yyyy) fits!