Checking Sitecore field type via FieldTypeManager.GetField()

gistfile1.cs

var field = item.Fields[_fieldId];
var type = FieldTypeManager.GetField(field);

if (type is LinkField)
{
	...
}
if (type is InternalLinkField)		// such as drop tree controls
{
	...
}
else if(type is MultilistField)
{
	...
}