public IEnumerable<DbColumnInfo> GetColumns(string providerName, string connectionString, string tableName)
{
    DbProviderFactory factory = DbProviderFactories.GetFactory(providerName);
    using (DbConnection connection = factory.CreateConnection())
    using (DbCommand command = factory.CreateCommand())
    {
        connection.ConnectionString = connectionString;
        connection.Open();
        command.Connection = connection;

        var columns = connection.GetSchema("Columns", tableName.Split('.'));
        foreach (DataRow row in columns.Rows)
        {
            yield return new DbColumnInfo()
            {
                Name = row.Field<string>(3),
                OrdinalPosition = row.Field<short>(4),
                DataType = this.FormatDataType(row),
                IsNullable = string.Equals(row.Field<string>(6), "yes", StringComparison.InvariantCultureIgnoreCase),
                IsPrimaryKey = // ... ?
            };
        }
    }
}

var da = factory.CreateDataAdapter();
    command.CommandText = "select * from Employees";
    da.SelectCommand = command;
    da.MissingSchemaAction = MissingSchemaAction.AddWithKey;

    var dtab = new DataTable();
    da.FillSchema(dtab, SchemaType.Source);

    foreach (DataColumn col in dtab.Columns)
    {
        string name = col.ColumnName;
        bool isNull = col.AllowDBNull;
        bool isPrimary = dtab.PrimaryKey.Contains(col);
    }

public IEnumerable<DbColumnInfo> GetColumns(string connectionString, DbTableInfo table)
{
    DbProviderFactory factory = DbProviderFactories.GetFactory(this.providerName);
    using (DbConnection connection = factory.CreateConnection())
    using (DbCommand command = factory.CreateCommand())
    {
        connection.ConnectionString = connectionString;
        connection.Open();
        command.Connection = connection;
        command.CommandText = ColumnInfoQuery;
        command.CommandType = CommandType.Text;
        var tableSchema = factory.CreateParameter();
        tableSchema.ParameterName = "@tableSchema";
        tableSchema.DbType = DbType.String;
        tableSchema.Value = table.Schema;
        command.Parameters.Add(tableSchema);
        var tableName = factory.CreateParameter();
        tableName.ParameterName = "@tableName";
        tableName.DbType = DbType.String;
        tableName.Value = table.Name;
        command.Parameters.Add(tableName);

        var dataTable = new DataTable();
        using (var reader = command.ExecuteReader())
        {
            while (reader.Read())
            {
                yield return new DbColumnInfo()
                {
                    Name = reader.GetString(0),
                    OrdinalPosition = reader.GetInt32(1),
                    DataType = reader.GetString(2),
                    IsNullable = reader.GetBoolean(3),
                    IsPrimaryKey = reader.GetBoolean(4),
                    IsForeignKey = reader.GetBoolean(5),
                    IsUnique = reader.GetBoolean(6),
                };
            }
        }
    }
}

string[] restrictions = new string[] { null, null,   strTable };
            DataTable tableInfo = Connection.GetSchema("IndexColumns", restrictions);

            if (tableInfo == null)
                throw new Exception("TableInfo null Error");

            foreach (DataRow test in tableInfo.Rows)
            {
                Console.WriteLine(test["column_name"]);
            }

DataTable indexes = conn.GetSchema("Indexes");
List<string> PrimaryKeys = new List<string>();
foreach (DataRow row in indexes.Rows)
  if (Convert.ToBoolean(row["PRIMARY_KEY"]))
    PrimaryKeys.Add(row["TABLE_NAME"] + "." + row["COLUMN_NAME"]);