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HOW TO: Not allow a user to add multiple items of a meeting at the same time & date in a Calendar list for a user in SharePoint 2010

HOW TO: Not allow a user to add multiple items of a meeting at the same time & date in a Calendar list for a user in SharePoint 2010

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This post is a contribution from Bharat Rathod, an engineer with the SharePoint Developer Support team.

By default, SharePoint 2010 allows you to add multiple items in the calendar for the same date and time.  Below screenshot shows that Meeting1 and Meeting2 occur at the same date and time for the same user.

image

In real world scenario, we do not let a user have multiple entries of meetings at the same date and time.  For example, Outlook warns the user of the clashes of the meeting that occur at the same date and time.

Here’s a sample feature that will prevent this from occurring in your Calendar list.

The Feature.xml file

<?xml version="1.0" encoding="utf-8"?>
<Feature Scope="Site"
  Title="Simple Event Handler Registration"
  Id="853A4952-122D-4F97-8239-A2B02FFFDA68"
  xmlns="http://schemas.microsoft.com/sharepoint/">
  <ElementManifests>
    <ElementManifest Location="Elements.xml"/>
  </ElementManifests>
</Feature>

The Elements.xml file

<?xml version="1.0" encoding="utf-8"?>
<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
  <Receivers ListTemplateId="106">
    <Receiver>
      <Name>doublemeeting</Name>
      <Type>ItemAdding</Type>
      <SequenceNumber>10001</SequenceNumber>
      <Assembly>doublemeeting, Version=1.0.0.0, Culture=neutral, PublicKeyToken=30c59cdee5e7a547</Assembly>
      <Class>doublemeeting.PreventDoubleBooking</Class>
      <Data></Data>
      <Filter></Filter>
    </Receiver>
    <Receiver>
      <Name>doublemeeting</Name>
      <Type>ItemUpdating</Type>
      <SequenceNumber>10001</SequenceNumber>
      <Assembly>doublemeeting, Version=1.0.0.0, Culture=neutral, PublicKeyToken=30c59cdee5e7a547</Assembly>
      <Class>doublemeeting.PreventDoubleBooking</Class>
      <Data></Data>
      <Filter></Filter>
    </Receiver>
  </Receivers>
</Elements>

And the complete code file

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.SharePoint;
 
namespace doublemeeting
{
    public class PreventDoubleBooking : SPItemEventReceiver
    {
        /// <summary>
        /// This event is triggered when the user adds a new item
        /// </summary>
        /// <param name="properties"></param>
        public override void ItemAdding(SPItemEventProperties properties)
        {
            //Our query string variable
            string strQuery = null;
 
            try
            {
                //Get the Sharepoint site instance
                using (SPWeb oWebsite = new SPSite(properties.SiteId).OpenWeb(properties.RelativeWebUrl))
                {
 
                    //Get the collection of properties for the Booking item
                    SPListItemCollection collItems = oWebsite.Lists[properties.ListTitle].Items;
 
                    //Get the Calendar List that we will be querying against
                    SPList calendar = oWebsite.Lists[properties.ListId];
 
                    //Get the internal name of the fields we are querying. 
                    //These are required for the CAML query
                    string start_internal = collItems.List.Fields["Start Time"].InternalName;
                    string end_internal = collItems.List.Fields["End Time"].InternalName;
                    string Category_Internal = collItems.List.Fields["Category"].InternalName;
 
                    //Get the query string parameters
                    string start_str = properties.AfterProperties[start_internal].ToString();
                    string end_str = properties.AfterProperties[end_internal].ToString();
                    string Category_str = properties.AfterProperties[Category_Internal].ToString();
 
                    //Construct a CAML query
                    SPQuery query = new SPQuery();
 
                    //Create the CAML query string that checks to see if the booking we are attemping
                    //to add will overlap any existing bookings
                    strQuery = string.Format(@"
 
    <Where>
    
        <And>
            <Or>
            
                <Or>
                    <And>
                       <Leq>
                          <FieldRef Name='EventDate' />
                          <Value Type='DateTime' IncludeTimeValue='TRUE'>{0}</Value>
                       </Leq>
 
                       <Gt>
                          <FieldRef Name='EndDate' />
                          <Value Type='DateTime' IncludeTimeValue='TRUE'>{0}</Value>
                       </Gt>
                    </And>
 
                    <And>
                       <Lt>
                          <FieldRef Name='EventDate' />
                          <Value Type='DateTime' IncludeTimeValue='TRUE'>{1}</Value>
                       </Lt>
 
                       <Geq>
                          <FieldRef Name='EndDate' />
                          <Value Type='DateTime' IncludeTimeValue='TRUE'>{1}</Value>
                       </Geq>
                    </And>
                </Or>
                
                <Or>
                    <And>
                       <Leq>
                          <FieldRef Name='EventDate' />
                          <Value Type='DateTime' IncludeTimeValue='TRUE'>{0}</Value>
                       </Leq>
 
                       <Geq>
                          <FieldRef Name='EndDate' />
                          <Value Type='DateTime' IncludeTimeValue='TRUE'>{1}</Value>
                       </Geq>
                    </And>
 
                    <And>
                       <Geq>
                          <FieldRef Name='EventDate' />
                          <Value Type='DateTime' IncludeTimeValue='TRUE'>{0}</Value>
                       </Geq>
 
                       <Leq>
                          <FieldRef Name='EndDate' />
                          <Value Type='DateTime' IncludeTimeValue='TRUE'>{1}</Value>
                       </Leq>
                    </And>
                </Or>
                
            </Or>
        
            <Eq>
                <FieldRef Name='Category' />
                <Value Type='Choice'>{2}</Value>
            </Eq>
            
        </And>
        
    </Where>
    <OrderBy>
        <FieldRef Name='EventDate' />
    </OrderBy>
", start_str, end_str, Category_str);
 
                    //Set the query string for the SPQuery object
                    query.Query = strQuery;
 
                    //Execute the query against the Calendar List
                    SPListItemCollection existing_events = calendar.GetItems(query);
 
                    //Check to see if the query returned any overlapping bookings
                    if (existing_events.Count > 0)
                    {
                        //Cancels the ItemAdd action and redirects to error page
                        properties.Cancel = true;
 
                        //Edit the error message that will display on the error page
                        properties.ErrorMessage += "This booking cannot be made because of one or more bookings in conflict. <BR><BR>";
 
                        //Here you can loop through the results of the query
                        //foreach (SPListItem oListItem in existing_events)
                        //{
                        //   ....
                        //}
 
                        properties.ErrorMessage += "Please go back and schedule a new time.";
                    }
 
                }
            }
            catch (Exception ex)
            {
                //Cancels the ItemAdd action and redirects to error page
                properties.Cancel = true;
 
                //Edit the error message that will display on the error page
                properties.ErrorMessage = "Error looking for booking conflicts: " + ex.Message;
            }
 
        }
 
        /// <summary>
        /// This event is triggered when the user edits an calendar item
        /// </summary>
        /// <param name="properties"></param>
        public override void ItemUpdating(SPItemEventProperties properties)
        {
 
            string strQuery = null;
 
            try
            {
 
                //Get the Sharepoint site instance
                using (SPWeb oWebsite = new SPSite(properties.SiteId).OpenWeb(properties.RelativeWebUrl))
                {
 
                    //Get the collection of properties for the Booking item
                    SPListItemCollection collItems = oWebsite.Lists[properties.ListTitle].Items;
 
                    //Get the Calendar List that we will be querying against
                    SPList calendar = oWebsite.Lists[properties.ListId];
 
                    //Get the internal name of the fields we are querying. 
                    //These are required for the CAML query
                    string start_internal = collItems.List.Fields["Start Time"].InternalName;
                    string end_internal = collItems.List.Fields["End Time"].InternalName;
                    string Category_Internal = collItems.List.Fields["Category"].InternalName;
                    string guid_internal = collItems.List.Fields["GUID"].InternalName;
 
                    //Get the query string parameters
                    string start_str = properties.AfterProperties[start_internal].ToString();
                    string end_str = properties.AfterProperties[end_internal].ToString();
                    string Category_str = properties.AfterProperties[Category_Internal].ToString();
                    string guid_str = properties.AfterProperties[guid_internal].ToString();
 
                    //Construct a CAML query
                    SPQuery query = new SPQuery();
 
                    //Create the CAML query string that checks to see if the booking we are attemping
                    //to change will overlap any existing bookings, OTHER THAN ITSELF
                    strQuery = string.Format(@"
 
    <Where>
        <And>
        
            <And>
                <Or>
                
                    <Or>
                        <And>
                           <Leq>
                              <FieldRef Name='EventDate' />
                              <Value Type='DateTime' IncludeTimeValue='TRUE'>{0}</Value>
                           </Leq>
 
                           <Gt>
                              <FieldRef Name='EndDate' />
                              <Value Type='DateTime' IncludeTimeValue='TRUE'>{0}</Value>
                           </Gt>
                        </And>
 
                        <And>
                           <Lt>
                              <FieldRef Name='EventDate' />
                              <Value Type='DateTime' IncludeTimeValue='TRUE'>{1}</Value>
                           </Lt>
 
                           <Geq>
                              <FieldRef Name='EndDate' />
                              <Value Type='DateTime' IncludeTimeValue='TRUE'>{1}</Value>
                           </Geq>
                        </And>
                    </Or>
                    
                    <Or>
                        <And>
                           <Leq>
                              <FieldRef Name='EventDate' />
                              <Value Type='DateTime' IncludeTimeValue='TRUE'>{0}</Value>
                           </Leq>
 
                           <Geq>
                              <FieldRef Name='EndDate' />
                              <Value Type='DateTime' IncludeTimeValue='TRUE'>{1}</Value>
                           </Geq>
                        </And>
 
                        <And>
                           <Geq>
                              <FieldRef Name='EventDate' />
                              <Value Type='DateTime' IncludeTimeValue='TRUE'>{0}</Value>
                           </Geq>
 
                           <Leq>
                              <FieldRef Name='EndDate' />
                              <Value Type='DateTime' IncludeTimeValue='TRUE'>{1}</Value>
                           </Leq>
                        </And>
                    </Or>
                    
                </Or>
            
                <Eq>
                    <FieldRef Name='Category' />
                    <Value Type='Choice'>{2}</Value>
                </Eq>
                
            </And>
        
            <Neq>
                <FieldRef Name='GUID' />
                <Value Type='GUID'>{3}</Value>
            </Neq>
        
        </And>
        
    </Where>
    
    <OrderBy>
        <FieldRef Name='EventDate' />
    </OrderBy>
", start_str, end_str, Category_str, guid_str);
 
                    //Set the query string for the SPQuery object
                    query.Query = strQuery;
 
                    //Execute the query against the Calendar List
                    SPListItemCollection existing_events = calendar.GetItems(query);
 
                    //Check to see if the query returned any overlapping bookings
                    if (existing_events.Count > 0)
                    {
 
                        //Cancels the ItemAdd action and redirects to error page
                        properties.Cancel = true;
 
                        //Edit the error message that will display on the error page
                        properties.ErrorMessage += "This booking cannot be made because of one or more bookings in conflict. <BR><BR>";
 
                        //Here you can loop through the results of the query
                        //foreach (SPListItem oListItem in existing_events)
                        //{
                        //   ....
                        //}
 
                        properties.ErrorMessage += "Please go back and schedule a new time.";
                    }
 
                }
            }
            catch (Exception ex)
            {
 
                //Cancels the ItemAdd action and redirects to error page
                properties.Cancel = true;
 
                //Edit the error message that will display on the error page
                properties.ErrorMessage = "Error looking for booking conflicts: " + ex.Message;
            }
 
        }
 
    }
}

Below are the source code and the feature file samples for your reference.

Sample source code: DoubleMeetingSource

Hope this post was helpful!

Comments
  • Many thanks for this post. This will allow me to use this in my office environment. I am just checking with you; is there any way we can link Outlook 2010 - room booking calendar with sharepoint calendar. Just a check.

    Cheers

    Sathya

  • See if this helps - www.ehow.com/how_5905423_publish-existing-outlook-calendar-sharepoint.html.

  • Hi

    Can you tell me please how can intall it in a sharepoint foundation?

    Thanks

  • Can you please provide some guidance on how this is deployed?

  • @Anahr: so, this is a custom Event Receiver solution which we are deploying. We would also need to modify the Feature.xml associated with the Feature and the Element.xml & code-behind files for the Event Receiver as mentioned above.

    For more details onto how to create a sample Event Receiver solution, you can refer this MSDN link:-  msdn.microsoft.com/.../gg252010(v=office.14).aspx

  • @TrevoR2300: You should be able to implement the same in a SP 2010 Foundation. For more details of Event Receivers in SP 2010 Foundation, you can refer this MSDN link:- msdn.microsoft.com/.../gg749858(v=office.14).aspx

  • Nice solution, but it will not work for new recurring events. You need to extract the RecurrenceData and parse it....

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