Check whether variable value is DateTime or not.

private void NumericCheckMethod()
{
    var inputString = "DotNetFunda";
    if (!IsDateTime(inputString))
    {
        MessageBox.Show("InValid DateTime.");
    }
    
    object inputObject = null;
    if (!IsDateTime(inputObject))
    {
        MessageBox.Show("Input is null");
    }

    var fundaUserId = DateTime.Now;
    if (IsDateTime(fundaUserId))
    {
        MessageBox.Show("Valid DateTime.");
    }
}

/// <summary>
/// Check whether a provided input is valid datetime or not.
/// </summary>
/// <param name="input"></param>
/// <returns>True: if input is DateTime type.</returns>
private bool IsDateTime(object input)
{
    var isNumeric = false;
    DateTime actualValue;
    if (input != null && DateTime.TryParse(input.ToString(), out actualValue))
    {
        isNumeric = true;
    }

    return isNumeric;
}