Database context and Return Dynamic Result Set in ASP.NET MVC

Question

In MVC 4 and EF 5 i want to run dynamic query.

var returndata = Context.Database.SqlQuery(Type, strsql, null);

i don\'t know, how many fie

Answer 1

I have recently stumbled upon this example:

http://www.markzhou.com/blog/post/2011/06/02/Use-dynamic-type-in-Entity-Framework-41-SqlQuery()-method.aspx

I haven't had the time to test it myself but it seems that it is possible with some additional work to construct the dynamic type.

In short you would want to do something like this:

  TypeBuilder builder = Program.CreateTypeBuilder(
                "MyDynamicAssembly", "MyModule", "MyType");
  Program.CreateAutoImplementedProperty(builder, "name", typeof(string));
  Program.CreateAutoImplementedProperty(builder, "type", typeof(string));
  Program.CreateAutoImplementedProperty(builder, "id", typeof(int));

  Type resultType = builder.CreateType();
  dynamic queryResult = context.Database.SqlQuery(
                    resultType, "SELECT * FROM sys.sysobjects");

Where TypeBuilder is described in details in the post I have attached.

Answer 2

Without knowing anything about the type that is returned, I think you might be out of luck.

If you know what patterns it might fall under, you could use some try { } catch () { }'s on interfaces that match those parameters on your otherwise dynamic query, but that seems like it might be a bit painful.

Answer 3

Adding to Petr Voborník's answer, dynamic query, I add dynamic insert of ResultSet, my application takes the dynamic query of all tables of the entire database, a chunk at a time and then inserts the dynamic results into a remote database, using Always Encrypted (omitted here). Passing a sb command and parameter object.

    public void StoreData(DbContext dbContext, Dictionary<string, string> columnInfo, List<Dictionary<string, object>> multiInsertObj, string tableName)
    {
        _ctx = dbContext;
        _columnInfo = columnInfo;
        var sb = new StringBuilder();
        sb.Append(BuildSqlCommand(tableName, columnInfo, multiInsertObj.Count));
        ExecuteSqlCommand(sb, GetParamsObject(columnInfo, multiInsertObj));
    }

    private static StringBuilder BuildSqlCommand(string tableName, Dictionary<string, string> variableInfo, int variableCount)
    {
        //Build sql command
        var sb = new StringBuilder();
        sb.Append("INSERT INTO dbo." + tableName + "(");
        foreach (var variable in variableInfo)
        {
            sb.Append(variable.Key);
            sb.Append(", ");
        }
        sb.Append("SystemNumber, ");
        sb.Remove(sb.Length - 2, 2).Append(") VALUES ");
        for (var i = 0; i < variableCount; i++)
        {
            sb.Append("(");
            foreach (var name in variableInfo.Keys)
            {
                sb.Append("@" + name + "_" + i + ",");
            }
            sb.Append("@SystemNumber" + "_" + i + ",");
            sb.Remove(sb.Length - 1, 1).Append("),");
        }
        sb.Remove(sb.Length - 1, 1);
        return sb;
    }

    private static object[] GetParamsObject(Dictionary<string, string> columnInfo, List<Dictionary<string, object>> multiInsertObj)
    {
        var variableCount = multiInsertObj.Count;
        var rowCount = multiInsertObj[0].Keys.Count;
        var objectLength = (rowCount + 1) * variableCount;
        var variableDataTypes = columnInfo.Values.ToList();
        var paramObj = new object[objectLength];
        var j = 0;
        var i = 0;
        foreach (var row in multiInsertObj)
        {
            var k = 0;
            foreach (var data in row)
            {
                var sb = new StringBuilder();
                sb.Append("@");
                sb.Append(data.Key);
                sb.Append("_" + i);
                paramObj[j] = new SqlParameter(sb.ToString(), SetSqlDataType(variableDataTypes[k])) { Direction = Input, Value = data.Value };
                j++;
                k++;
            }
            paramObj[j] = new SqlParameter(("@SystemNumber" + "_" + i), SetSqlDataType("int")) { Direction = Input, Value = _systemNumber };
            i++;
            j++;
        }
        return paramObj;
    }

    private static void ExecuteSqlCommand(StringBuilder sb, params object[] sqlParameters)
    {
        using (_ctx)
        {
            _ctx.Database.Connection.Open();
            using (var cmd = _ctx.Database.Connection.CreateCommand())
            {
                cmd.CommandText = sb.ToString();
                foreach (var param in sqlParameters)
                    cmd.Parameters.Add(param);
                try
                {
                    cmd.ExecuteNonQuery();
                }
                catch (Exception e)
                {
                    Console.WriteLine(e);
                    throw;
                }
            }
        }
    }

Answer 4

This method loads data from SQL select (with parameters) to the list of rows, where each row is the dictionary of columns (the key is the column name).

private static List<Dictionary<string, object>> LoadData(string sqlSelect, params object[] sqlParameters)
{
    var table = new List<Dictionary<string, object>>();
    using (var ctx = new DbEntities())
    {
        ctx.Database.Connection.Open();
        using (var cmd = ctx.Database.Connection.CreateCommand())
        {
            cmd.CommandText = sqlSelect;
            foreach (var param in sqlParameters)
                cmd.Parameters.Add(param);
            using (var reader = cmd.ExecuteReader())
            {
                while (reader.Read())
                {
                    var row = new Dictionary<string, object>();
                    for (int i = 0; i < reader.FieldCount; i++)
                        row[reader.GetName(i)] = reader[i];
                    table.Add(row);
                }
            }
        }
    }
    return table;
}

Answer 5

Similarly post by Darin Dimitrov, but it returns DataTable

public DataTable QueryToTable(Entities db, string queryText, SqlParameter[] parametes)
        {
            using ( DbDataAdapter adapter = new SqlDataAdapter())
            {
                adapter.SelectCommand = db.Database.Connection.CreateCommand();
                adapter.SelectCommand.CommandText = queryText;
                if (parametes != null)
                    adapter.SelectCommand.Parameters.AddRange(parametes);
                DataTable table = new DataTable();
                adapter.Fill(table);
                return table;
            }
        }

Use

SqlParameter[] parametes = new[]
                {
                    new SqlParameter("date_from", dateFrom)
                };

DataTable tab = QueryToTable(new Entities(), 
               "Select *  From SomeTable Where ADate >= @date_from", parametes);

Example for MS SQL Server

Answer 6

Unfortunately, EF won't materialize objects unless it knows their Type.

If this is really necessary for you, I think your best bet would be to fall back to ADO.NET and DataTable.