VAR.DatabaseExplorer/VAR.DatabaseExplorer/Code/DataAccess/ColumnDA.cs

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using VAR.DatabaseExplorer.Code.DataTransfer;

namespace VAR.DatabaseExplorer.Code.DataAccess
{
    public class ColumnDA
    {
        public static List<Column> GetColumns(string conexionString, string tableSchema, string tableName)
        {
            var columns = new List<Column>();
            var cnx = new SqlConnection(conexionString);

            // Preparar comando y parametros
            var da = new SqlDataAdapter(@"
                SELECT  col.COLUMN_NAME AS ColumnName,
                        col.DATA_TYPE AS Type,
                        col.CHARACTER_MAXIMUM_LENGTH AS Size,
                        c.CONSTRAINT_TYPE AS KeyType,
                        col.IS_NULLABLE AS Nullable
                    FROM INFORMATION_SCHEMA.COLUMNS AS col
                    LEFT JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS k
                        ON  col.COLUMN_NAME=k.COLUMN_NAME AND
                            col.TABLE_NAME=k.TABLE_NAME AND
                            col.TABLE_SCHEMA=k.TABLE_SCHEMA
                    LEFT JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS c
                        ON k.CONSTRAINT_NAME=c.CONSTRAINT_NAME
                    WHERE   col.TABLE_NAME=@TableName AND
                           col.TABLE_SCHEMA=@TableSchema
                    ORDER BY col.ORDINAL_POSITION
                ", cnx);
            var prm = new SqlParameter("@TableName", SqlDbType.VarChar, 100) { Value = tableName };
            da.SelectCommand.Parameters.Add(prm);
            prm = new SqlParameter("@TableSchema", SqlDbType.VarChar, 100) { Value = tableSchema };
            da.SelectCommand.Parameters.Add(prm);

            // Obtener datatable con las columnas
            var dt = new DataTable();
            cnx.Open();
            da.Fill(dt);
            cnx.Close();

            // Recorrer datatable estableciendo la lista de columnas
            foreach (DataRow dr in dt.Rows)
            {
                string columnName = Convert.ToString(dr["ColumnName"]);
                Column col = columns.FirstOrDefault(c => c.Name == columnName);
                if (col == null)
                {
                    col = new Column();
                    columns.Add(col);
                }

                col.Name = columnName;

                col.Type = Convert.ToString(dr["Type"]);

                if ((dr["Size"] is DBNull) == false)
                {
                    col.Size = Convert.ToInt32(dr["Size"]);
                }

                string strNullable = (Convert.ToString(dr["Nullable"])).ToLower();
                col.Nullable = (strNullable == "yes") || (strNullable == "1") || (strNullable == "true");

                string KeyType = Convert.ToString(dr["KeyType"]).ToLower();
                if (KeyType.Contains("primary"))
                {
                    col.PK = true;
                }
            }

            return columns;
        }
    }
}