How to set the internal name for a SPField in SharePoint 2010?

Question

I add fields to a list programmaticly. The following line adds a new field´to an existing List

Lists.AddFieldToList(warrantyList, SPFieldType.Text, "internalFieldName", "ShownFieldName", "Comment", false, false, false);                    

This is the method that is called:

public static bool AddFieldToList(SPList list, SPFieldType fieldType, string fieldInternalName, string fieldDisplayName, string fieldDescription, bool unique, bool required, bool indexed)
    {
        SPField field = new SPField(list.ParentWeb.Fields, fieldType.ToString(), fieldInternalName);             
        bool success = AddFieldToList(list, field, fieldDisplayName, fieldDescription, unique, required, indexed);
        return success;
    }

after the first line of the method the field is filled with a lot of information, but no internalName(NULL) and a Title that contains "internalFieldName".

In the second line the following method is called:

  public static bool AddFieldToList(SPList list, SPField field, string fieldDisplayName, string fieldDescription, bool unique, bool required, bool indexed)
    {
        if (field != null &&
            (!list.Fields.Contains(field.Id)))
        {

            field.ReadOnlyField = false;
            field.Title = fieldDisplayName;
            field.Description = fieldDescription;
            field.EnforceUniqueValues = unique;
            field.Indexed = indexed;
            field.Required = required;
            list.Fields.Add(field);
            return true;
        }

        return false;
    }

After that the title is changed to "ShownFieldName" (of course). But my goal is to have an internalname "internalFieldName" which has a Displayname "ShownFieldName", so "ShownFieldName" is shown in the List but I can access the item by the internal name

as field.InternalName is readOnly: How can I solve that issue?

Answer 1

This line creates an SPField object that could have the internal name you need ( displayName passed to the constructor equals fieldInternalName ):

SPField field = new SPField(list.ParentWeb.Fields, fieldType.ToString(), fieldInternalName);

but before anything has been saved to the database you change it in this line:

field.Title = fieldDisplayName;

Here's the solution:

1. Add a field to the list passing internalFieldName as both fieldInternalName and fieldDisplayName .
2. Call the SPList.Update() method.
3. Get the field reference from the list and change its Title property to ShownFieldName .
4. Call the SPField.Update() method.

Answer 2

They have a method AddFieldAsXml in SharePoint since SharePoint 2007. If you do that, you get more control over how you are adding the fields. See an example in the link above.