How to Validate a DateTime in C

Question

I doubt I am the only one who has come up with this solution  but if you have a better one please post it here  I simply want to leave this question here so I and others can search it later    I needed to tell whether a valid date had been entered into a text box and this is the code that I came up with  I fire this when focus leaves the text box   try       DateTime Parse startDateTextBox Text     catch       startDateTextBox Text   DateTime Today ToShortDateString

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I would use the DateTime TryParse   method  http   msdn microsoft com en-us library system datetime tryparse aspx

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What about using TryParse

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You can also define the DateTime format for a specific CultureInfo  public static bool IsDateTime string tempDate        DateTime fromDateValue      var formats   new      MM dd yyyy    dd MM yyyy h mm ss    MM dd yyyy hh mm tt    yyyy - MM - dd T HH   mm   ss         return DateTime TryParseExact tempDate  formats  System Globalization CultureInfo InvariantCulture  System Globalization DateTimeStyles None  out fromDateValue

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One liner  if  DateTime TryParse value  out        dostuff

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A problem with using DateTime TryParse is that it doesn t support the very common data-entry use case of dates entered without separators  e g  011508   Here s an example of how to support this    This is from a framework I m building  so its signature is a little weird  but the core logic should be usable        private static readonly Regex ShortDate   new Regex     d 6          private static readonly Regex LongDate   new Regex     d 8           public object Parse object value  out string message                msg   null          string s   value ToString   Trim            if  s Trim                                return null                    else                       if  ShortDate Match s  Success                                s   s Substring 0  2          s Substring 2  2          s Substring 4  2                             if  LongDate Match s  Success                                s   s Substring 0  2          s Substring 2  2          s Substring 4  4                             DateTime d   DateTime MinValue              if  DateTime TryParse s  out d                                 return d                            else                               message   String Format     0    is not a valid date    s                   return null

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All the Answers are Quite great but if you want to use a single function  this may work   private bool validateTime string dateInString        DateTime temp      if  DateTime TryParse dateInString  out temp                return true            return false

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protected bool ValidateBirthday String date                DateTime Temp           if  DateTime TryParse date  out Temp     true  amp  amp        Temp Hour    0  amp  amp        Temp Minute    0  amp  amp        Temp Second    0  amp  amp        Temp Millisecond    0  amp  amp        Temp  gt  DateTime MinValue              return true          else             return false            suppose that input string is short date format   e g   2013 7 5  returns true or   2013 2 31  returns false   http   forums asp net t 1250332 aspx 1        bool booleanValue   ValidateBirthday  12 55    returns false

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protected static bool CheckDate DateTime date        if new DateTime      date                return false             else                 return true

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A problem with using DateTime TryParse is that it doesn t support the very common data-entry use case of dates entered without separators  e g  011508   Here s an example of how to support this    This is from a framework I m building  so its signature is a little weird  but the core logic should be usable        private static readonly Regex ShortDate   new Regex     d 6          private static readonly Regex LongDate   new Regex     d 8           public object Parse object value  out string message                msg   null          string s   value ToString   Trim            if  s Trim                                return null                    else                       if  ShortDate Match s  Success                                s   s Substring 0  2          s Substring 2  2          s Substring 4  2                             if  LongDate Match s  Success                                s   s Substring 0  2          s Substring 2  2          s Substring 4  4                             DateTime d   DateTime MinValue              if  DateTime TryParse s  out d                                 return d                            else                               message   String Format     0    is not a valid date    s                   return null

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Don t use exceptions for flow control  Use DateTime TryParse and DateTime TryParseExact  Personally I prefer TryParseExact with a specific format  but  I guess there are times when TryParse is better  Example use based on your original code   DateTime value  if   DateTime TryParse startDateTextBox Text  out value         startDateTextox Text   DateTime Today ToShortDateString        Reasons for preferring this approach    Clearer code  it says what it wants to do  Better performance than catching and swallowing exceptions This doesn t catch exceptions inappropriately - e g  OutOfMemoryException  ThreadInterruptedException   Your current code could be fixed to avoid this by just catching the relevant exception  but using TryParse would still be better

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Don t use exceptions for flow control  Use DateTime TryParse and DateTime TryParseExact  Personally I prefer TryParseExact with a specific format  but  I guess there are times when TryParse is better  Example use based on your original code   DateTime value  if   DateTime TryParse startDateTextBox Text  out value         startDateTextox Text   DateTime Today ToShortDateString        Reasons for preferring this approach    Clearer code  it says what it wants to do  Better performance than catching and swallowing exceptions This doesn t catch exceptions inappropriately - e g  OutOfMemoryException  ThreadInterruptedException   Your current code could be fixed to avoid this by just catching the relevant exception  but using TryParse would still be better

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DateTime TryParse   This I believe is faster and it means you dont have to use ugly try catches     e g  DateTime temp  if DateTime TryParse startDateTextBox Text  out temp          Yay      else        Aww

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A problem with using DateTime TryParse is that it doesn t support the very common data-entry use case of dates entered without separators  e g  011508   Here s an example of how to support this    This is from a framework I m building  so its signature is a little weird  but the core logic should be usable        private static readonly Regex ShortDate   new Regex     d 6          private static readonly Regex LongDate   new Regex     d 8           public object Parse object value  out string message                msg   null          string s   value ToString   Trim            if  s Trim                                return null                    else                       if  ShortDate Match s  Success                                s   s Substring 0  2          s Substring 2  2          s Substring 4  2                             if  LongDate Match s  Success                                s   s Substring 0  2          s Substring 2  2          s Substring 4  4                             DateTime d   DateTime MinValue              if  DateTime TryParse s  out d                                 return d                            else                               message   String Format     0    is not a valid date    s                   return null

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What about using TryParse

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private void btnEnter Click object sender  EventArgs e        maskedTextBox1 Mask    00 00 0000       maskedTextBox1 ValidatingType   typeof System DateTime         if   IsValidDOB maskedTextBox1 Text        if   ValidateBirthday maskedTextBox1 Text           MessageBox Show   Not Valid        else         MessageBox Show  Valid         check date format dd mm yyyy  but not if year  lt  1 or  gt  2013  public static bool IsValidDOB string dob         DateTime temp      if  DateTime TryParse dob  out temp           return  true       else          return  false        checks date format dd mm yyyy and year  gt  1900   protected bool ValidateBirthday String date        DateTime Temp      if  DateTime TryParse date  out Temp     true  amp  amp          Temp Year  gt  1900  amp  amp            Temp Hour    0  amp  amp  Temp Minute    0  amp  amp            Temp Second    0  amp  amp  Temp Millisecond    0  amp  amp          Temp  gt  DateTime MinValue          return  true       else         return  false

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One liner  if  DateTime TryParse value  out        dostuff

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private void btnEnter Click object sender  EventArgs e        maskedTextBox1 Mask    00 00 0000       maskedTextBox1 ValidatingType   typeof System DateTime         if   IsValidDOB maskedTextBox1 Text        if   ValidateBirthday maskedTextBox1 Text           MessageBox Show   Not Valid        else         MessageBox Show  Valid         check date format dd mm yyyy  but not if year  lt  1 or  gt  2013  public static bool IsValidDOB string dob         DateTime temp      if  DateTime TryParse dob  out temp           return  true       else          return  false        checks date format dd mm yyyy and year  gt  1900   protected bool ValidateBirthday String date        DateTime Temp      if  DateTime TryParse date  out Temp     true  amp  amp          Temp Year  gt  1900  amp  amp            Temp Hour    0  amp  amp  Temp Minute    0  amp  amp            Temp Second    0  amp  amp  Temp Millisecond    0  amp  amp          Temp  gt  DateTime MinValue          return  true       else         return  false

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DateTime TryParse   This I believe is faster and it means you dont have to use ugly try catches     e g  DateTime temp  if DateTime TryParse startDateTextBox Text  out temp          Yay      else        Aww

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DateTime TryParse   This I believe is faster and it means you dont have to use ugly try catches     e g  DateTime temp  if DateTime TryParse startDateTextBox Text  out temp          Yay      else        Aww

User · Answer

I would use the DateTime TryParse   method  http   msdn microsoft com en-us library system datetime tryparse aspx

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All the Answers are Quite great but if you want to use a single function  this may work   private bool validateTime string dateInString        DateTime temp      if  DateTime TryParse dateInString  out temp                return true            return false

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DateTime temp  try       temp   Convert ToDateTime grd Rows e RowIndex  Cells  dateg   Value       grd Rows e RowIndex  Cells  dateg   Value   temp ToString  yyyy MM dd      catch           MessageBox Show  Sorry The date not valid    Error   MessageBoxButtons OK  MessageBoxIcon Stop MessageBoxDefaultButton Button1 MessageBoxOptions  RightAlign       grd Rows e RowIndex  Cells  dateg   Value   null

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DateTime TryParse   This I believe is faster and it means you dont have to use ugly try catches     e g  DateTime temp  if DateTime TryParse startDateTextBox Text  out temp          Yay      else        Aww

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Here s another variation of the solution that returns true if the string can be converted to a DateTime type  and false otherwise   public static bool IsDateTime string txtDate        DateTime tempDate      return DateTime TryParse txtDate  out tempDate

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What about using TryParse

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protected static bool CheckDate DateTime date        if new DateTime      date                return false             else                 return true

User · Answer

What about using TryParse

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Don t use exceptions for flow control  Use DateTime TryParse and DateTime TryParseExact  Personally I prefer TryParseExact with a specific format  but  I guess there are times when TryParse is better  Example use based on your original code   DateTime value  if   DateTime TryParse startDateTextBox Text  out value         startDateTextox Text   DateTime Today ToShortDateString        Reasons for preferring this approach    Clearer code  it says what it wants to do  Better performance than catching and swallowing exceptions This doesn t catch exceptions inappropriately - e g  OutOfMemoryException  ThreadInterruptedException   Your current code could be fixed to avoid this by just catching the relevant exception  but using TryParse would still be better

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Here s another variation of the solution that returns true if the string can be converted to a DateTime type  and false otherwise   public static bool IsDateTime string txtDate        DateTime tempDate      return DateTime TryParse txtDate  out tempDate

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DateTime temp  try       temp   Convert ToDateTime date       date   temp ToString  yyyy MM dd      catch        MessageBox Show  Sorry The date not valid    Error   MessageBoxButtons OK  MessageBoxIcon Stop MessageBoxDefaultButton Button1 MessageBoxOptions  RightAlign       date   null

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protected bool ValidateBirthday String date                DateTime Temp           if  DateTime TryParse date  out Temp     true  amp  amp        Temp Hour    0  amp  amp        Temp Minute    0  amp  amp        Temp Second    0  amp  amp        Temp Millisecond    0  amp  amp        Temp  gt  DateTime MinValue              return true          else             return false            suppose that input string is short date format   e g   2013 7 5  returns true or   2013 2 31  returns false   http   forums asp net t 1250332 aspx 1        bool booleanValue   ValidateBirthday  12 55    returns false

User · Answer

A problem with using DateTime TryParse is that it doesn t support the very common data-entry use case of dates entered without separators  e g  011508   Here s an example of how to support this    This is from a framework I m building  so its signature is a little weird  but the core logic should be usable        private static readonly Regex ShortDate   new Regex     d 6          private static readonly Regex LongDate   new Regex     d 8           public object Parse object value  out string message                msg   null          string s   value ToString   Trim            if  s Trim                                return null                    else                       if  ShortDate Match s  Success                                s   s Substring 0  2          s Substring 2  2          s Substring 4  2                             if  LongDate Match s  Success                                s   s Substring 0  2          s Substring 2  2          s Substring 4  4                             DateTime d   DateTime MinValue              if  DateTime TryParse s  out d                                 return d                            else                               message   String Format     0    is not a valid date    s                   return null

User · Answer

Don t use exceptions for flow control  Use DateTime TryParse and DateTime TryParseExact  Personally I prefer TryParseExact with a specific format  but  I guess there are times when TryParse is better  Example use based on your original code   DateTime value  if   DateTime TryParse startDateTextBox Text  out value         startDateTextox Text   DateTime Today ToShortDateString        Reasons for preferring this approach    Clearer code  it says what it wants to do  Better performance than catching and swallowing exceptions This doesn t catch exceptions inappropriately - e g  OutOfMemoryException  ThreadInterruptedException   Your current code could be fixed to avoid this by just catching the relevant exception  but using TryParse would still be better

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DateTime temp  try       temp   Convert ToDateTime grd Rows e RowIndex  Cells  dateg   Value       grd Rows e RowIndex  Cells  dateg   Value   temp ToString  yyyy MM dd      catch           MessageBox Show  Sorry The date not valid    Error   MessageBoxButtons OK  MessageBoxIcon Stop MessageBoxDefaultButton Button1 MessageBoxOptions  RightAlign       grd Rows e RowIndex  Cells  dateg   Value   null

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DateTime temp  try       temp   Convert ToDateTime date       date   temp ToString  yyyy MM dd      catch        MessageBox Show  Sorry The date not valid    Error   MessageBoxButtons OK  MessageBoxIcon Stop MessageBoxDefaultButton Button1 MessageBoxOptions  RightAlign       date   null

User · Answer

I would use the DateTime TryParse   method  http   msdn microsoft com en-us library system datetime tryparse aspx

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You can also define the DateTime format for a specific CultureInfo  public static bool IsDateTime string tempDate        DateTime fromDateValue      var formats   new      MM dd yyyy    dd MM yyyy h mm ss    MM dd yyyy hh mm tt    yyyy - MM - dd T HH   mm   ss         return DateTime TryParseExact tempDate  formats  System Globalization CultureInfo InvariantCulture  System Globalization DateTimeStyles None  out fromDateValue

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I would use the DateTime TryParse   method  http   msdn microsoft com en-us library system datetime tryparse aspx

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