How do I extract the type from a field?

Question

In SharePoint Server side code, you can write something like:

field.fieldvalueType

Which will sometimes give you the type (DateTime, or whatever). Annoyingly, sometimes, it just returns Null (for example, the ID field).

In CSOM, you don't have that field. However, there's TypeAsString which gives SharePoint types such as:

• Computed
• Integer
• Note

What I'd like to do is grab this huge table from MSDN:

And Extract "Int32" when I know that I'm dealing with an "Integer" field, and extract "System.String" from SharePoint's note.

This kinda works, but it's the mother of all hacks:

var myTempItem = list.AddItem(new ListItemCreationInformation());
myTempItem.Update();
context.ExecuteQuery();

context.Load(myTempItem);
context.ExecuteQuery();

After creation, you can use:

myTempItemCreated[fieldImTryingToGetTypeOf.Title].GetType().FullName -> Gives-> System.Int32

Now, what's the proper way to do it? I'm just hoping the answer isn't a ten foot long switch case statement.

Answer 1

Expanding on @Vadim's answer, here is a version that does not construct a new dictionary every time the extension method is called;

namespace SharePoint.Client.Extensions
{
    public static class FieldExtensions
    {
        private static Dictionary<FieldType, Type> _fieldTypes = new Dictionary<FieldType, Type>()
        {
            { FieldType.Guid, typeof(Guid) },
            { FieldType.Attachments, typeof(bool)},
            {FieldType.Boolean, typeof(bool)},
            {FieldType.Choice, typeof(string)},
            {FieldType.CrossProjectLink, typeof(bool)},
            {FieldType.DateTime, typeof(DateTime)},
            {FieldType.Lookup, typeof(FieldLookupValue)},
            {FieldType.ModStat, typeof(int)},
            {FieldType.MultiChoice, typeof(string[])},
            {FieldType.Number, typeof(double)},
            {FieldType.Recurrence, typeof(bool)},
            {FieldType.Text, typeof(string)},
            {FieldType.URL, typeof(FieldUrlValue)},
            {FieldType.User, typeof(FieldUserValue)},
            {FieldType.WorkflowStatus, typeof(int)},
            {FieldType.ContentTypeId, typeof(ContentTypeId)},
            {FieldType.Note, typeof(string)},
            {FieldType.Counter, typeof(int)},
            {FieldType.Computed, typeof(string)},
            {FieldType.Integer, typeof(int)},
            {FieldType.File, typeof(string)}
        };

        public static Type GetFieldValueType(this Field field)
        {
            if (!_fieldTypes.ContainsKey(field.FieldTypeKind))
                throw new NotSupportedException(string.Format("Unknown field type: {0}", field.FieldTypeKind));
            return _fieldTypes[field.FieldTypeKind];
        }
    }
}

Answer 2

Since there is no SPField.FieldValueType property counterparts in SharePoint CSOM API, the following extension method demonstrates how to perform it:

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.SharePoint.Client;
using Field = Microsoft.SharePoint.Client.Field;

namespace SharePoint.Client.Extensions
{
    public static class FieldExtensions
    {


        public static Type GetFieldValueType(this Field field)
        {
            var table = new Dictionary<FieldType, Type>();
            table[FieldType.Guid] = typeof(Guid);
            table[FieldType.Attachments] = typeof(bool);
            table[FieldType.Boolean] = typeof(bool);
            table[FieldType.Choice] = typeof (string);
            table[FieldType.CrossProjectLink] = typeof(bool);
            table[FieldType.DateTime] = typeof(DateTime);
            table[FieldType.Lookup] = typeof(FieldLookupValue);
            table[FieldType.ModStat] = typeof(int);
            table[FieldType.MultiChoice] = typeof(string[]);
            table[FieldType.Number] = typeof(double);
            table[FieldType.Recurrence] = typeof(bool);
            table[FieldType.Text] = typeof(string);
            table[FieldType.URL] = typeof(FieldUrlValue);
            table[FieldType.URL] = typeof(FieldUrlValue);
            table[FieldType.User] = typeof(FieldUserValue);
            table[FieldType.WorkflowStatus] = typeof(int);
            table[FieldType.ContentTypeId] = typeof(ContentTypeId);
            table[FieldType.Note] = typeof(string);
            table[FieldType.Counter] = typeof(int);
            table[FieldType.Computed] = typeof(string);
            table[FieldType.Integer] = typeof(int);
            table[FieldType.File] = typeof(string);

            if (!table.ContainsKey(field.FieldTypeKind))
                throw new NotSupportedException(string.Format("Unknown field type: {0}", field.FieldTypeKind));
            return table[field.FieldTypeKind];
        }
    }
}

Usage

var list = ctx.Web.Lists.GetByTitle(listTitle);
var fields = list.Fields;
ctx.Load(fields);
ctx.ExecuteQuery();

foreach (var field in fields)
{
    if (field.FieldTypeKind != FieldType.Invalid)
    {
         var fieldValueType = field.GetFieldValueType();
         Console.WriteLine("{0} : {1}", field.InternalName, fieldValueType);    
    }        
}

Answer 3

Generally, you need to do the mapping you describe, not the myTempItemCreated[fieldImTryingToGetTypeOf.Title].GetType().FullName method.

The reason is, myTempItemCreated[fieldImTryingToGetTypeOf.Title].GetType().FullName will fail in the scenario where the field value (e.g. Title) is null for that particular ListItem object. (While Title is not generally null, other fields can be and are null). And obviously null does not give you an object on which you can call the GetType() method (you would get a NullReferenceException obviously).

So, for a general solution to the problem, one does indeed have to map the String returned from TypeAsString of the list field, calling from the list object / list field, and not from the list item.

Answer 4

You can get the type of field using the following snippet:

item.Fields["Title"].FieldValueType.FullName