GetSchemaMockup

GetSchemaMockup.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;


namespace SchemaMockup.Console
{
    using System.Data.Common;
    using System.Data.SqlClient;
    using PostgreClient;

    class Program
    {
        static void Main(string[] args)
        {
            //if it is called from sql client
            ProcessSomething(new SqlCommand().ExecuteReader());
            ProcessSomething(new PostgreDataReader());

            //or you can callit directly from sqldatareader
            var colSchema = new SqlCommand().ExecuteReader().GetColumnSchema();

        }

        //you can access it in data reader
        static void ProcessSomething(DbDataReader reader)
        {
            //this will replace reader.GetSchemaTable();
            var columnSchema = reader.GetColumnSchema();
        }
    }
}


namespace System.Data.Common
{

    public static class DbReaderExtension
    {

        //this is will be exposed to the client application   
        public static Collection<DbColumn> GetColumnSchema(this DbDataReader reader)
        {
            return DbSchemaGenerator.Generators[reader.GetType()]().GetColumnSchema(reader);
        }
    }

    public abstract class DbSchemaGenerator
    {

        //this is internal only DataCommon and access this
        internal static Dictionary<Type, Func<DbSchemaGenerator>> Generators = new Dictionary<Type, Func<DbSchemaGenerator>>();
        public static void RegisterDbSchemaGenerator(Type dbReaderType, Func<DbSchemaGenerator> constuctorDelegate)
        {
            Generators.Add(dbReaderType, constuctorDelegate);
        }


        public abstract Collection<DbColumn> GetColumnSchema(DbDataReader reader);
    }


    #region <<Not important stuff>>
    public class DbColumn { }
    #endregion
}

namespace System.Data.SqlClient
{
    using System.Data.Common;

    //this can be internal which no one can create this generator except the client
    internal class SqlDbSchemaGenerator : DbSchemaGenerator
    {
        static SqlDbSchemaGenerator()
        {
            //Register this Generator
            RegisterDbSchemaGenerator(typeof(SqlDataReader), () =>
            {
                return new SqlDbSchemaGenerator();
            });
        }

        public override Collection<DbColumn> GetColumnSchema(DbDataReader reader)
        {
            //implement sql schema specifically.
            throw new NotImplementedException();
        }
    }
}

namespace PostgreClient
{
    using System.Collections;
    using System.Data.Common;

    //this can be internal which no one can create this generator except the client
    internal class PostgreDbSchemaGenerator : DbSchemaGenerator
    {
        static PostgreDbSchemaGenerator()
        {
            //Register this Generator
            RegisterDbSchemaGenerator(typeof(PostgreDataReader), () =>
            {
                return new PostgreDbSchemaGenerator("Some parameter");
            });
        }

        private PostgreDbSchemaGenerator(string param)
        {
            //creat custom param
        }

        public override Collection<DbColumn> GetColumnSchema(DbDataReader reader)
        {
            //implement sql schema specifically.
            throw new NotImplementedException();
        }

    }

    #region <<not important stuff>>
    //just to mock postgre Data reader
    public class PostgreDataReader : DbDataReader { public override object this[string name] { get { throw new NotImplementedException(); } } public override object this[int ordinal] { get { throw new NotImplementedException(); } } public override int Depth { get { throw new NotImplementedException(); } } public override int FieldCount { get { throw new NotImplementedException(); } } public override bool HasRows { get { throw new NotImplementedException(); } } public override bool IsClosed { get { throw new NotImplementedException(); } } public override int RecordsAffected { get { throw new NotImplementedException(); } } public override bool GetBoolean(int ordinal) { throw new NotImplementedException(); } public override byte GetByte(int ordinal) { throw new NotImplementedException(); } public override long GetBytes(int ordinal, long dataOffset, byte[] buffer, int bufferOffset, int length) { throw new NotImplementedException(); } public override char GetChar(int ordinal) { throw new NotImplementedException(); } public override long GetChars(int ordinal, long dataOffset, char[] buffer, int bufferOffset, int length) { throw new NotImplementedException(); } public override string GetDataTypeName(int ordinal) { throw new NotImplementedException(); } public override DateTime GetDateTime(int ordinal) { throw new NotImplementedException(); } public override decimal GetDecimal(int ordinal) { throw new NotImplementedException(); } public override double GetDouble(int ordinal) { throw new NotImplementedException(); } public override IEnumerator GetEnumerator() { throw new NotImplementedException(); } public override Type GetFieldType(int ordinal) { throw new NotImplementedException(); } public override float GetFloat(int ordinal) { throw new NotImplementedException(); } public override Guid GetGuid(int ordinal) { throw new NotImplementedException(); } public override short GetInt16(int ordinal) { throw new NotImplementedException(); } public override int GetInt32(int ordinal) { throw new NotImplementedException(); } public override long GetInt64(int ordinal) { throw new NotImplementedException(); } public override string GetName(int ordinal) { throw new NotImplementedException(); } public override int GetOrdinal(string name) { throw new NotImplementedException(); } public override string GetString(int ordinal) { throw new NotImplementedException(); } public override object GetValue(int ordinal) { throw new NotImplementedException(); } public override int GetValues(object[] values) { throw new NotImplementedException(); } public override bool IsDBNull(int ordinal) { throw new NotImplementedException(); } public override bool NextResult() { throw new NotImplementedException(); } public override bool Read() { throw new NotImplementedException(); } };
    #endregion
}