How can I generate database tables from C# classes?

Question

Does anyone know a way to auto-generate database tables for a given class? I\'m not looking for an entire persistence layer - I already have a data access solution I\'m usi

Answer 1

It's really late, and I only spent about 10 minutes on this, so its extremely sloppy, however it does work and will give you a good jumping off point:

using System;
using System.Collections.Generic;
using System.Text;
using System.Reflection;

namespace TableGenerator
{
    class Program
    {
        static void Main(string[] args)
        {
            List tables = new List();

            // Pass assembly name via argument
            Assembly a = Assembly.LoadFile(args[0]);

            Type[] types = a.GetTypes();

            // Get Types in the assembly.
            foreach (Type t in types)
            {
                TableClass tc = new TableClass(t);                
                tables.Add(tc);
            }

            // Create SQL for each table
            foreach (TableClass table in tables)
            {
                Console.WriteLine(table.CreateTableScript());
                Console.WriteLine();
            }

            // Total Hacked way to find FK relationships! Too lazy to fix right now
            foreach (TableClass table in tables)
            {
                foreach (KeyValuePair field in table.Fields)
                {
                    foreach (TableClass t2 in tables)
                    {
                        if (field.Value.Name == t2.ClassName)
                        {
                            // We have a FK Relationship!
                            Console.WriteLine("GO");
                            Console.WriteLine("ALTER TABLE " + table.ClassName + " WITH NOCHECK");
                            Console.WriteLine("ADD CONSTRAINT FK_" + field.Key + " FOREIGN KEY (" + field.Key + ") REFERENCES " + t2.ClassName + "(ID)");
                            Console.WriteLine("GO");

                        }
                    }
                }
            }
        }
    }

    public class TableClass
    {
        private List> _fieldInfo = new List>();
        private string _className = String.Empty;

        private Dictionary dataMapper
        {
            get
            {
                // Add the rest of your CLR Types to SQL Types mapping here
                Dictionary dataMapper = new Dictionary();
                dataMapper.Add(typeof(int), "BIGINT");
                dataMapper.Add(typeof(string), "NVARCHAR(500)");
                dataMapper.Add(typeof(bool), "BIT");
                dataMapper.Add(typeof(DateTime), "DATETIME");
                dataMapper.Add(typeof(float), "FLOAT");
                dataMapper.Add(typeof(decimal), "DECIMAL(18,0)");
                dataMapper.Add(typeof(Guid), "UNIQUEIDENTIFIER");

                return dataMapper;
            }
        }

        public List> Fields
        {
            get { return this._fieldInfo; }
            set { this._fieldInfo = value; }
        }

        public string ClassName
        {
            get { return this._className; }
            set { this._className = value; }
        }

        public TableClass(Type t)
        {
            this._className = t.Name;

            foreach (PropertyInfo p in t.GetProperties())
            {
                KeyValuePair field = new KeyValuePair(p.Name, p.PropertyType);

                this.Fields.Add(field);
            }
        }

        public string CreateTableScript()
        {
            System.Text.StringBuilder script = new StringBuilder();

            script.AppendLine("CREATE TABLE " + this.ClassName);
            script.AppendLine("(");
            script.AppendLine("\t ID BIGINT,");
            for (int i = 0; i < this.Fields.Count; i++)
            {
                KeyValuePair field = this.Fields[i];

                if (dataMapper.ContainsKey(field.Value))
                {
                    script.Append("\t " + field.Key + " " + dataMapper[field.Value]);
                }
                else
                {
                    // Complex Type? 
                    script.Append("\t " + field.Key + " BIGINT");
                }

                if (i != this.Fields.Count - 1)
                {
                    script.Append(",");
                }

                script.Append(Environment.NewLine);
            }

            script.AppendLine(")");

            return script.ToString();
        }
    }
}

I put these classes in an assembly to test it:

public class FakeDataClass
{
    public int AnInt
    {
        get;
        set;
    }

    public string AString
    {
        get;
        set;
    }

    public float AFloat
    {
        get;
        set;
    }

    public FKClass AFKReference
    {
        get;
        set;
    }
}

public class FKClass
    {
        public int AFKInt
        {
            get;
            set;
        }
    }

And it generated the following SQL:

CREATE TABLE FakeDataClass
(
         ID BIGINT,
         AnInt BIGINT,
         AString NVARCHAR(255),
         AFloat FLOAT,
         AFKReference BIGINT
)


CREATE TABLE FKClass
(
         ID BIGINT,
         AFKInt BIGINT
)


GO
ALTER TABLE FakeDataClass WITH NOCHECK
ADD CONSTRAINT FK_AFKReference FOREIGN KEY (AFKReference) REFERENCES FKClass(ID)
GO

Some further thoughts...I'd consider adding an attribute such as [SqlTable] to your classes, that way it only generates tables for the classes you want. Also, this can be cleaned up a ton, bugs fixed, optimized (the FK Checker is a joke) etc etc...Just to get you started.