How can I generate database tables from C# classes?
Asked Answered
N

12

66

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 using, but I suddenly have to store a lot of information from a large number of classes and I really don't want to have to create all these tables by hand. For example, given the following class:

class Foo
{
    private string property1;
    public string Property1
    {
        get { return property1; }
        set { property1 = value; }
    }

    private int property2;
    public int Property2
    {
        get { return property2; }
        set { property2 = value; }
    }
}

I'd expect the following SQL:

CREATE TABLE Foo
(
    Property1 VARCHAR(500),
    Property2 INT
)

I'm also wondering how you could handle complex types. For example, in the previously cited class, if we changed that to be :

class Foo
{
    private string property1;
    public string Property1
    {
        get { return property1; }
        set { property1 = value; }
    }

    private System.Management.ManagementObject property2;
    public System.Management.ManagementObject Property2
    {
        get { return property2; }
        set { property2 = value; }
    }
}

How could I handle this?

I've looked at trying to auto-generate the database scripts by myself using reflection to enumerate through each class' properties, but it's clunky and the complex data types have me stumped.

Nimwegen answered 6/9, 2008 at 3:52 Comment(1)
even I am looking for the same solution. Could you please help me to generate sql tables from class's. ?Currey
P
112

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<TableClass> tables = new List<TableClass>();

            // 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<String, Type> 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<KeyValuePair<String, Type>> _fieldInfo = new List<KeyValuePair<String, Type>>();
        private string _className = String.Empty;

        private Dictionary<Type, String> dataMapper
        {
            get
            {
                // Add the rest of your CLR Types to SQL Types mapping here
                Dictionary<Type, String> dataMapper = new Dictionary<Type, string>();
                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<KeyValuePair<String, Type>> 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<String, Type> field = new KeyValuePair<String, Type>(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<String, Type> 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.

Preparedness answered 6/9, 2008 at 5:50 Comment(5)
I can't believe I used this in 2016. Thanks so much for this!Milksop
2019 - checking inEnumeration
This is great start point for creating table from C# class. If someone need docs about SQL datatype to CLR type mapping below is link from Microsoft. learn.microsoft.com/en-us/dotnet/framework/data/adonet/sql/linq/…Junta
how to Pass assembly name via argument?Ancillary
Even in last days of 2023 :D @MilksopTrail
A
13

@Jonathan Holland

Wow, I think that's the most raw work I've ever seen put into a StackOverflow post. Well done. However, instead of constructing DDL statements as strings, you should definitely use the SQL Server Management Objects classes introduced with SQL 2005.

David Hayden has a post entitled Create Table in SQL Server 2005 Using C# and SQL Server Management Objects (SMO) - Code Generation that walks through how to create a table using SMO. The strongly-typed objects make it a breeze with methods like:

// Create new table, called TestTable
Table newTable = new Table(db, "TestTable");

and

// Create a PK Index for the table
Index index = new Index(newTable, "PK_TestTable");
index.IndexKeyType = IndexKeyType.DriPrimaryKey;

VanOrman, if you're using SQL 2005, definitely make SMO part of your solution.

Andreasandree answered 6/9, 2008 at 11:33 Comment(1)
Great suggestion. Never seen this before. Your link is broken, but here's another example: codeproject.com/Articles/127065/…Alit
B
4

Try out my CreateSchema extension method for objects at http://createschema.codeplex.com/

It returns a string for any object containing CREATE TABLE scripts.

Blaeberry answered 5/4, 2012 at 18:15 Comment(0)
E
3

I think for complex data types, you should extend them by specifying a ToDB() method which holds their own implementation for creating tables in the DB, and this way it becomes auto-recursive.

Edom answered 6/9, 2008 at 5:52 Comment(0)
C
3

As of 2016 (I think), you can use Entity Framework 6 Code First to generate SQL schema from poco c# classes or to use Database First to generate c# code from sql. Code First to DB walkthrough

Chellean answered 3/10, 2016 at 16:26 Comment(0)
S
1

For complex types, you can recursively convert each one that you come across into a table of its own and then attempt to manage foreign key relationships.

You may also want to pre-specify which classes will or won't be converted to tables. As for complex data that you want reflected in the database without bloating the schema, you can have one or more tables for miscellaneous types. This example uses as many as 4:

CREATE TABLE MiscTypes /* may have to include standard types as well */
 ( TypeID INT,
   TypeName VARCHAR(...)
 )

CREATE TABLE MiscProperties
 ( PropertyID INT,
   DeclaringTypeID INT, /* FK to MiscTypes */
   PropertyName VARCHAR(...),
   ValueTypeID INT /* FK to MiscTypes */
 )

CREATE TABLE MiscData
 (  ObjectID INT,
    TypeID  INT
 )

CREATE TABLE MiscValues
 ( ObjectID INT, /* FK to MiscData*/
   PropertyID INT,
   Value VARCHAR(...)
 )
Shire answered 6/9, 2008 at 4:18 Comment(0)
E
0

Also... maybe you can use some tool such as Visio (not sure if Visio does this, but I think it does) to reverse engineer your classes into UML and then use the UML to generate the DB Schema... or maybe use a tool such as this http://www.tangiblearchitect.net/visual-studio/

Edom answered 6/9, 2008 at 5:56 Comment(0)
C
0

I know you're looking for an entire persistence layer, but NHibernate's hbm2ddl task can do this almost as a one-liner.

There is a NAnt task available to call it which may well be of interest.

Coincidentally answered 6/9, 2008 at 9:14 Comment(0)
B
0

Subsonic is also another option. I often use it to generate entity classes that map to a database. It has a command line utility that lets you specify tables, types, and a host of other useful things

Bussell answered 7/9, 2008 at 4:44 Comment(0)
K
0

There is a free app, Schematrix which generates classes from DB, check out if does the reverse too :) http://www.schematrix.com/products/schemacoder/download.aspx

Knickknack answered 24/5, 2015 at 3:17 Comment(0)
M
-1

Try DaoliteMappingTool for .net. It can help you generate the classes. Download form Here

Montparnasse answered 6/1, 2009 at 2:2 Comment(0)
R
-2

You can do the opposite, database table to C# classes here: http://pureobjects.com/dbCode.aspx

Reaper answered 15/4, 2009 at 4:27 Comment(1)
Title = "How can I generate database tables from C # classes?", Why would He want to do the opposite?Inverter

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