If you have some links, please add them in the comments

“Failed to enable constraints. One or more rows  contain values violating non-null, unique, or foreign-key  constraints.”

when using ADO.NET Datasets ?

Tthis is an incredibly useful message isn’t it ?

So what can you do to spare you some headaches ? Retrieve a more useful message sure !

You have to know that a Datatable object have a “HasError” property, this property allows you to know if the datatable has one ore more rows in error.

When HasError is true, you can retrieve the rows havin an error with the DataTable’s “GetErrors()” method wich return an array with all datarow having an error.

The “in errror” rows can inform you about errors with the “RowError” property.

Here is a simple helper class which can be used to debug a single DataTable or an entire DataSet:

using System;
using System.Data;

public class DataSetErrorRevealer
{

   /// <summary>
   /// Get errors on rows of a DataTable
   /// </summary>
   /// <param name="errorDataTable">The DataTable to be checked</param>
   public static void RevealTableErrors(DataTable errorDataTable)
   {
      if (errorDataTable == null)
      {
         Console.WriteLine("The provided DataTable object is null");
         return;
      }

      if (errorDataTable.HasErrors)
      {
         DataRow[] rowsInError = errorDataTable.GetErrors();
         if (rowsInError.Length <= 0)
         {
            Console.WriteLine("There is no problem with table {0}", errorDataTable.TableName);
         }
         else
         {
            foreach (DataRow errorRow in rowsInError)
            {
               Console.WriteLine(errorRow.RowError);
            }
         }
      }
   }

   /// <summary>
   /// Get errors on row for all tables of a DataSet
   /// </summary>
   /// <param name="errorDataSet">The Dataset to be checked</param>
   public static void RevealDataSetErrors(DataSet errorDataSet)
   {
         if (errorDataSet == null)
         {
            Console.WriteLine("The provided DataSet is null");
            return;
         }

         foreach (DataTable errorTable in errorDataSet.Tables)
         {
            RevealTableErrors(errorTable);
         }
      }
   }

Use it this way :

   TestDataSet dataset = new TestDataSet();
   try
   {
      using (SqlConnection sqlCon = new SqlConnection("MyConnectionString"))
      {
         SqlCommand sqlComm = sqlCon.CreateCommand();
         sqlComm.CommandType = CommandType.StoredProcedure;
         sqlComm.CommandText = "Select Stored procedure";
         SqlDataAdapter sqlDa = new SqlDataAdapter(sqlComm);
         sqlDa.Fill(dataset);
      }
   }
   catch (Exception ex)
   {
   // Will provide the error message :
   // "Failed to enable constraints. One or more rows
   // contain values violating non-null, unique,
   // or foreign-key  constraints."
   Console.WriteLine("Error : {0}", ex);

   // will provide a more helpful message
   DataSetErrorRevealer.RevealDataSetErrors(dataset);
   }

If you prefer, you can use an extension method :

using System.Data;
using System;

public static class DataSetExtensions
{
   public static void RevealErrors(this DataSet errorDataSet)
   {
      if (errorDataSet == null)
      {
         Console.WriteLine("The provided DataSet is null");
         return;
      }

      foreach (DataTable errorTable in errorDataSet.Tables)
      {
         errorTable.RevealErrors();
      }
   }

   public static void RevealErrors(this DataTable errorDataTable)
   {
      if (errorDataTable == null)
      {
         Console.WriteLine("The provided DataTable object is null");
         return;
      }

      if (errorDataTable.HasErrors)
      {
         DataRow[] rowsInError = errorDataTable.GetErrors();
         if (rowsInError.Length <= 0)
         {
            Console.WriteLine("There is no problem with table {0}", errorDataTable.TableName);
         }
         else
         {
            foreach (DataRow errorRow in rowsInError)
            {
               Console.WriteLine(errorRow.RowError);
            }
         }
      }
   }
}

use :

catch (Exception ex)
{
   // will provide an helpful message
   dataset.RevealErrors();
}

Hope this helps !

If you want to set the ControlToValidate property of an ASP.NET validator to the DateTimeControl’s ID, it will throw an error!
As you can guess, you have to target the controls inside the DateTimeControl.

Since the DateTimeControl set the name of the controls programmatically, you can retrieve the id of the control:

• Textbox date: DateTimeControl.ID +”Date”
• Dropdownlist hours: DateTimeControl.ID +”DateHours”
• Dropdownlist minutes: DateTimeControl.ID +”DateMinutes”

Example:

If you use the SharePoint:DateTimeControl with the TimeOnly property set to “true”

<SharePoint:DateTimeControl runat="server" ID="TheTime" TimeOnly="true"/>

You’ll have two dropdownlists, one for the hours and one for the minutes
The DateTimeControl set the name:

Dropdownlist hours: DateTimeControl.ID +”DateHours”

Html will be:

<select name="ctl00$PlaceHolderMain$ctl07$ctl02$TheTime$TheTimeDateHours" id="ctl00_PlaceHolderMain_ctl07_ctl02_TheTime_TheTimeDateHours" dir="ltr">
 <option value="00:">00:</option>
 <option value="01:">01:</option>
 <option value="02:">02:</option>
 <option value="03:">03:</option>
 <option value="04:">04:</option>
 <option value="05:">05:</option>
 <option value="06:">06:</option>
 <option value="07:">07:</option>
 <option value="08:">08:</option>
 <option value="09:">09:</option>
 <option value="10:">10:</option>
 <option value="11:">11:</option>
 <option value="12:">12:</option>
 <option value="13:">13:</option>
 <option value="14:">14:</option>
 <option value="15:">15:</option>
 <option value="16:">16:</option>
 <option value="17:">17:</option>
 <option value="18:">18:</option>
 <option value="19:">19:</option>
 <option value="20:">20:</option>
 <option value="21:">21:</option>
 <option value="22:">22:</option>
 <option value="23:">23:</option>
</select>

Dropdownlist minutes: DateTimeControl.ID +”DateMinutes”
Html will be:

<select name="ctl00$PlaceHolderMain$ctl07$ctl02$TheTime$TheTimeDateMinutes" id="ctl00_PlaceHolderMain_ctl07_ctl02_TheTime_TheTimeDateMinutes" dir="ltr">
 <option value="00">00</option>
 <option value="05">05</option>
 <option value="10">10</option>
 <option value="15">15</option>
 <option value="20">20</option>
 <option value="25">25</option>
 <option value="30">30</option>
 <option value="35">35</option>
 <option value="40">40</option>
 <option value="45">45</option>
 <option value="50">50</option>
 <option value="55">55</option>
</select>

So you can retrieve the ASP.NET controls by using :

• For the date: TheTime$TheTimeDate
• For the hours: TheTime$TheTimeDateHours
• For the minutes: TheTime$TheTimeDateMinutes

Real case example:

I have two DateTimeControl, one named TheStartTime and one other named TheEndTime,

I want to validate that the end time is not before the start time.

So I’ll use the ASP.NET comparevalidator validator to compare the hours:

<asp:CompareValidator id="valDate" runat="server" ControlToValidate="TheEndTime$TheEndTimeDateHours" ControlToCompare="TheStartTime$TheStartTimeDateHours"
 Type="Integer"
 Operator="GreaterThanEqual"
 ErrorMessage="The end time must be greater than the start time">
 </asp:CompareValidator >

Now, if you want to validate both hours and minutes, one option is to add an “asp:CustomValidator” and check conditions server side :
Markup:

<asp:CustomValidator runat="server" ID="EndTimeMustBeLaterThanStartTimeCustomValidator"
EnableClientScript="false" ErrorMessage="Start time must be before end time"/>

Before the action, validate:

if (!IsEndTimeLaterThanStartTime())
{
 EndTimeMustBeLaterThanStartTimeCustomValidator.IsValid = false;
 return;
}

Validation method:

private bool IsEndTimeLaterThanStartTime()
{
 // retrieve the DropDownList
 DropDownList startHours = TheStartTime.FindControl("TheStartTimeDateHours") as DropDownList;
 DropDownList endHours = TheEndTime.FindControl("TheEndTimeDateHours") as DropDownList;

 // prevent from errors
 if (startHours == null ||
 endHours == null ||
 string.IsNullOrEmpty(startHours.SelectedValue) ||
 string.IsNullOrEmpty(endHours.SelectedValue))
 {
 return; // dont' do anything
 }

// the hour value is "00:"
 int startHour = Convert.ToInt32(startHours.SelectedValue.Replace(":",""));
 int endHour = Convert.ToInt32(endHours.SelectedValue.Replace(":", ""));
 if (endHour < startHour)
 {
 args.IsValid = false;
 }
 else
 {

 if (endHour == startHour)
 {
 // check the minutes
 DropDownList startMinutes = TheStartTime.FindControl("TheStartTimeDateMinutes") as DropDownList;
 DropDownList endMinutes = TheEndTime.FindControl("TheEndTimeDateMinutes") as DropDownList;
 // prevent from errors
 if (startMinutes == null ||
 endMinutes == null ||
 string.IsNullOrEmpty(startMinutes.SelectedValue) ||
 string.IsNullOrEmpty(endMinutes.SelectedValue))
 {
 return; // dont' do anything
 }

 int startMinute = Convert.ToInt32(startMinutes.SelectedValue);
 int endMinute = Convert.ToInt32(endMinutes.SelectedValue);

 if (endHour <= startMinute)
 args.IsValid = false;

 }
 }

 args.IsValid = true;

 }

You can also validate the Date himself if you choose to display it,
you can make a client side validation if you know javascript,
you can do everything like in “classic” ASP.NET.

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string String1 = "testString";
if (String1== null || String1 == "")
{
// ...
}
else
{
// ...
}

string String1 = "testString";
 if (String1 == null || String1.Length==0)
 {
 // ...
 }
 else
 {
 // ...
 }

 string String1 = "testString";
 if (string.IsNullOrEmpty(String1))
 {
 // ...
 }
 else
 {
 // ...
 }

The last one is more readable.

But what about performances ?

Check this code :

private void CheckForNullOrEmpty()
 {
 int maxIterations = 9999999;

 Console.WriteLine("if (string.IsNullOrEmpty(String1))");
 Stopwatch watch = Stopwatch.StartNew();
 for (int i = 0; i < maxIterations; i++)
 {
 string String1 = "testString";
 if (string.IsNullOrEmpty(String1))
 {
 // ...
 }
 else
 {
 // ...
 }
 }

 watch.Stop();
 Console.WriteLine("\tTime : " + watch.Elapsed.TotalMilliseconds);
 Console.WriteLine(Environment.NewLine);

 Console.WriteLine("if (String1== null || String1 == \"\"");
 watch = Stopwatch.StartNew();
 for (int i = 0; i < maxIterations; i++)
 {
 string String1 = "testString";
 if (String1 == null || String1 == "")
 {
 // ...
 }
 else
 {
 // ...
 }
 }

 watch.Stop();
 Console.WriteLine("\tTime : " + watch.Elapsed.TotalMilliseconds);
 Console.WriteLine(Environment.NewLine);

 Console.WriteLine("if (String1 == null || String1.Length==0)");
 watch = Stopwatch.StartNew();
 for (int i = 0; i < maxIterations; i++)
 {
 string String1 = "testString";
 if (String1 == null || String1.Length == 0)
 {
 // ...
 }
 else
 {
 // ...
 }
 }

 watch.Stop();
 Console.WriteLine("\tTime : " + watch.Elapsed.TotalMilliseconds);
 Console.WriteLine(Environment.NewLine);

 Console.WriteLine(Environment.NewLine);
 Console.WriteLine("Press any key to continue");
 Console.ReadLine();
 }

Output is :

The difference between “String.IsNullOrEmpty” and “check for null then for lenght” is minimal, so prefer the String.IsNullOrEmpty() wich is more readable.

As you can guess, IsNullOrEmpty performs a check for null, then a check for lenght :

If you use Reflector to inspect the String class in the mscorlib, you can see that String.IsNullOrEmpty do the same thing we do in our test :

public static bool IsNullOrEmpty(string value)
{
if (value != null)
{
return (value.Length == 0);
}
return true;
}

the “extra” time comes from the method call

Note : In .Net Framework 4.0: string.IsNullOrWhiteSpace() method appears, but I've not tested yet (link)

using System.Diagnostics;

// ...

Stopwatch myStopWatch = Stopwatch.StartNew();

// some code

myStopWatch.Stop();

Console.WriteLine("{0} ms - {1} ticks", myStopWatch.Elapsed.TotalMilliseconds, myStopWatch.ElapsedTicks);

// ...