Programmatically creating a field from the Custom field type

Environment: SharePoint Server 2013

Requirement: Programmatically create a field/column from a custom field type.

Following is a simple example with sample code to create a field from custom field type. In this example we are creating a custom field type (derived from SPFieldNumber) and add it to document library.

Note: I would recommend to refer to this MSDN post before this post to understand the entire steps involved to create a custom field type.

Creating the Custom Field Class.

The following example defines a custom control for displaying the custom field of type SPFieldNumber. The example overrides the OnAdded method to contain the logic while adding the custom field type in library/list.

using Microsoft.SharePoint;

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace Prasath.SP

{

   class SampleHitCountField: SPFieldNumber

   {

       public SampleHitCountField(SPFieldCollection fields, string fieldName)

           : base(fields, fieldName)

       {

       }

       public SampleHitCountField(SPFieldCollection fields, string typeName, string displayName)

           : base(fields, typeName, displayName)

       {

       }

       //Event triggered when new field is added to the document library

       public override void OnAdded(SPAddFieldOptions op)

       {

           base.OnAdded(op);

           Update();

           //Hide the field from new and edit form

           this.ShowInEditForm = false;

           this.ShowInNewForm = false;

           this.DefaultValue = "0";

           this.EnforceUniqueValues = false;

           this.Required = false;

           this.Update();

       }

   }

}

Creating the Field Type Definition

The following example registers the custom field type. This file must be named in the format fldtypes*.xml

<?xml version="1.0" encoding="utf-8" ?>

<FieldTypes>

 <FieldType>

   <Field Name="TypeName">SampleHitCountField</Field>

   <Field Name="TypeDisplayName">Total View Count</Field>

   <Field Name="InternalType">SampleHitCountField</Field>

   <Field Name="TypeShortDescription">Total View Count</Field>

   <Field Name="FieldTypeClass">Prasath.SP.SampleHitCountField, $SharePoint.Project.AssemblyFullName$</Field>

   <Field Name="ParentType">Number</Field>

   <Field Name="Sortable">TRUE</Field>

   <Field Name="Filterable">TRUE</Field>

   <Field Name="UserCreatable">TRUE</Field>

   <Field Name="ShowOnListCreate">FALSE</Field>

   <Field Name="ShowOnSurveyCreate">FALSE</Field>

   <Field Name="ShowOnDocumentLibrary">TRUE</Field>

   <Field Name="ShowOnColumnTemplateCreate">TRUE</Field>

   <Field Name="ShowInListSettings">TRUE</Field>

 </FieldType>

</FieldTypes>

Creating a Field from custom Field Type

Following is the method to create field from custom type

/// <summary>

       /// Create custom field as XML

       /// </summary>

       /// <param name="oId">Field GUID</param>

       /// <param name="strDisplayName">Unique Display Name of field</param>

       /// <param name="Required">Field required property</param>

       /// <param name="strFieldType">Custom field type</param>

       /// <param name="strFieldName">Custom field display name</param>

       /// <returns>string</returns>

       internal static string GetCreateFieldAsXml(Guid oId, string strDisplayName, bool Required, string strFieldType, string strFieldName)

       {

           XmlElement element = new XmlDocument().CreateElement("Field"); // Creating the “Field” element for the Inner XML schema

           element.SetAttribute("ID", oId.ToString()); // Setting the GUID of the field from value passed

           element.SetAttribute("Type", strFieldType); // Setting the Parent Type name of custom type registered in the “Fldtypes*.xml” file

           element.SetAttribute("Name", strFieldName); // Setting the Type Display Name registered in the “Fldtypes*.xml” file

           element.SetAttribute("DisplayName", strDisplayName); // Any unique Display Name

           element.SetAttribute("Required", Required.ToString().ToUpper());

           return element.OuterXml; // Returning the OuterXML to create the field as XML

       }

//Code to custom field as XML from custom field type

String strFieldasXML = GetCreateFieldAsXml(Guid.NewGuid(), “Hit Count Field”, false, "SampleHitCountField", “SampleHitCountField”);

web.Fields.AddFieldAsXml(strFieldasXML); //here 'web' is a SPWeb object