MapInfo Pro Developers User Group

I did like this, hope this helps

private void butSetSymStart_Click(object sender, EventArgs e)
        {
            miSymbol sym = new miSymbol();
            sym.setSymbolStyle(rwNet.P2PStartSym);
            _application.RunMapBasicCommand("run menu command " + dotNetMap.mapinfo.M_FORMAT_PICK_SYMBOL);
            sym.setSymbolPropertiesFromCurrent();
            rwNet.P2PStartSym = sym.makeSymbolCommand;
        }

Note M_FORMAT_PICK_SYMBOL = 503   I had setup as defines.

I had create a class

namespace dotNetMap
{
    public interface ImiSymbol
    {
        Int32 Symbol
        {
            get;
            set;
        }

        Int32 Colour
        {
            get;
            set;
        }

        Int32 Size
        {
            get;
            set;
        }

        Int32 shapeFromCurrent
        {
            get;
        }

        Int32 sizeFromCurrent
        {
            get;
        }

        Int32 colourFromCurrent
        {
            get;
        }

        string makeSymbolCommand
        {
            get;
            set;
        }
    }

    public class miSymbol : mapinfo, ImiSymbol
    {
        internal Int32 m_Shape = 0;
        internal Int32 m_Colour = 0;
        internal Int32 m_Size = 0;

        internal string m_MakeSymbolCommand = string.Empty;

        public string makeSymbolCommand
        {
            set
            {
                m_MakeSymbolCommand = value;
            }
            get
            {
                return m_MakeSymbolCommand;
            }
        }

        public Int32 Symbol
        {
            get
            {
                return m_Shape;
            }
            set
            {
                m_Shape = value;
            }
        }

        public Int32 Colour
        {
            get
            {
                return m_Colour;
            }
            set
            {
                m_Colour = value;
            }
        }

        public Int32 Size
        {
            get
            {
                return m_Size;
            }
            set
            {
                m_Size = value;
            }
        }

        public Int32 shapeFromCurrent
        {
            get
            {
                string command = string.Format(@"StyleAttr(CurrentSymbol(),{0})", SYMBOL_CODE);
                Int32 shape = Convert.ToInt32(Eval(command));
                return shape;
            }
        }

        public Int32 sizeFromCurrent
        {
            get
            {
                string command = string.Format(@"StyleAttr(CurrentSymbol(),{0})", SYMBOL_POINTSIZE);
                Int32 size = Convert.ToInt32(Eval(command));
                return size;
            }
        }

        public Int32 colourFromCurrent
        {
            get
            {
                string command = string.Format(@"StyleAttr(CurrentSymbol(),{0})", SYMBOL_COLOR);
                Int32 colour = Convert.ToInt32(Eval(command));
                return colour;
            }
        }

        public void setSymbolPropertiesFromCurrent()
        {
            m_Shape = shapeFromCurrent;
            m_Size = sizeFromCurrent;
            m_Colour = colourFromCurrent;

            m_MakeSymbolCommand = string.Format("makesymbol({0},{1},{2})", m_Shape, m_Colour, m_Size);

            //setSymbolStyle();
        }

        public void setSymbolStyle()
        {
            string command = string.Format("Set style symbol makesymbol({0},{1},{2})", m_Shape, m_Colour, m_Size);
            Do(command);
        }

        public void setSymbolStyle(Int32 symbol, Int32 colour, Int32 size)
        {
            m_Shape = symbol;
            m_Colour = colour;
            m_Size = size;

            setSymbolStyle();
        }

        public void setSymbolStyle(string makeSymbol)
        {
            m_MakeSymbolCommand = makeSymbol;
            setSymbolStyleFromCommand();
        }

        public void setSymbolStyleFromCommand()
        {
            Do("Set style symbol " + m_MakeSymbolCommand);
        }
    }
}