SQL Class Shell Generator

using System;
using System.Collections.Generic;
using System.Text;
using System.ComponentModel;
using System.Globalization;

namespace SQLReader
{
    public class ExpandableObject : ExpandableObjectConverter
    {
        private string getDataSize(long Length)
        {
            if (Length < 1024)
                return Length.ToString() + " bytes";
            else if (Length > 1023 && Length < 1048576)
                return ((long)(Length / 1024)).ToString() + " Kb";
            else if (Length > 1048575 && Length < 1073741824)
                return ((long)(Length / 1048576)).ToString() + " Mb";
            else if (Length > 1073741823 && Length < 1099511626752)
                return ((long)(Length / 1073741824)).ToString() + " Gb";
            else
                return ((long)(Length / 1099511626752)).ToString() + " Tb";
        }

        public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
        {
            if (destinationType == typeof(string))
            {
                if (value is Database)
                {
                    if (((Database)value).Tables.Items.Length > 0)
                    {
                        long totsize = 0;
                        foreach (Table t in ((Database)value).Tables.Items)
                            totsize += (t.DataUsageSize + t.IndexUsageSize) + t.UnusedSize;
                        return ((Database)value).name + " [" + getDataSize(totsize) + "]";
                    }
                    else
                        return ((Database)value).name;
                }
                if (value is Table)
                    return ((Table)value).name;
                if (value is Index)
                    return ((Index)value).name;
                if (value is IndexColumn)
                    return ((IndexColumn)value).Column.name;
                if (value is foreign_key)
                    return ((foreign_key)value).name;
                if (value is foreign_key_column)
                {
                    StringBuilder sb = new StringBuilder();
                    sb.Append(((foreign_key_column)value).ParentTable.name);
                    sb.Append(".");
                    sb.Append(((foreign_key_column)value).ParentColumn.name);
                    sb.Append(" - ");
                    sb.Append(((foreign_key_column)value).ReferencedTable.name);
                    sb.Append(".");
                    sb.Append(((foreign_key_column)value).ReferencedColumn.name);
                    return sb.ToString();
                }
                if (value is Column)
                    return ((Column)value).name;
                if (value is DatabaseFile)
                {
                    if(((DatabaseFile)value).size.HasValue)
                        return ((DatabaseFile)value).name + " [" + getDataSize(((DatabaseFile)value).size.Value) + "]";
                    else
                        return ((DatabaseFile)value).name + " []";
                }
                if (value is SQL_Type)
                {
                    return ((SQL_Type)value).name;
                }
                if (value is DefaultConstraint)
                {
                    return ((DefaultConstraint)value).definition;
                }
                if (value is Trigger)
                {
                    return ((Trigger)value).name;
                }
                if (value is Comment)
                {
                    if (((Comment)value).text.Length > 20)
                    {
                        if (((Comment)value).text.Contains(" "))
                        {
                            if (((Comment)value).text.IndexOf(" ", 10) < 30 && ((Comment)value).text.IndexOf(" ", 10) > 10)
                                return ((Comment)value).text.Substring(0, ((Comment)value).text.IndexOf(" ", 10)) + "...";
                            else if (((Comment)value).text.IndexOf(" ") < 20)
                                return ((Comment)value).text.Substring(0, ((Comment)value).text.IndexOf(" ")) + "...";
                            else
                                return ((Comment)value).text.Substring(0, 20) + "...";
                        }
                        else
                            return ((Comment)value).text;
                    }
                    else
                        return ((Comment)value).text;
                }
                if (value is IdentityColumn)
                    return "[" + ((IdentityColumn)value).increment_value.ToString() + "," + ((IdentityColumn)value).seed_value.ToString() + "]";
                if (value is Schema)
                    return ((Schema)value).name;
                if (value is User)
                    return ((User)value).name;
                if (value is ExtendedProperty)
                    return ((ExtendedProperty)value).value;
                if (value is KeyConstraint)
                    return ((KeyConstraint)value).name;
                if (value is View)
                    return ((View)value).name;
            }
            return base.ConvertTo(context, culture, value, destinationType);
        }
    }
}