无效的强制转换异常

Question

I am posting this because the last time I asked this question it did not get solved and I cannot seem to solve this on my own. I am very very new to C# and programming, trying to teach myself so and help you can give would be great.

So on to the error:

Unable to cast object of type 'System.Collections.Generic.List 1[test.Form1+comoditys]' to type 'System.Collections.Generic.List 1[test.Form2+mycost]'.

form2 code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;

namespace test
{
public partial class Form2 : Form
{
    public float Alligor;
    public float Briochit;
    public float Chollonin;
    public float Espitium;
    public float Hydrobenol;
    public float Isopropenetol;
    public float Metachropin;
    public float Phlobotil;
    public float Plasteosine;
    public float Polynitrocol;
    public float Polynucleit;
    public float Prilumium;
    public float Statchanol;
    public float Titanium;
    public float Vitricyl;

    public float AlligorInput;
    public float BriochitInput;
    public float CholloninInput;
    public float EspitiumInput;
    public float HydrobenolInput;
    public float IsopropenetolInput;
    public float MetachropinInput;
    public float PhlobotilInput;
    public float PlasteosineInput;
    public float PolynitrocolInput;
    public float PolynucleitInput;
    public float PrilumiumInput;
    public float StatchanolInput;
    public float TitaniumInput;
    public float VitricylInput;

    public float costofAlligor;
    public float costofBriochit;
    public float costofChollonin;
    public float costofEspitium;
    public float costofHydrobenol;
    public float costofIsopropenetol;
    public float costofMetachropin;
    public float costofPhlobotil;
    public float costofPlasteosine;
    public float costofPolynitrocol;
    public float costofPolynucleit;
    public float costofPrilumium;
    public float costofStatchanol;
    public float costofTitanium;
    public float costofVitricyl;

    public double totalCost;

    [Serializable]
    public class mycost
    {
        public float secondPrice;
    }

    private List<mycost> costList = new List<mycost>();

    private mycost o1 = null;
    private mycost o2 = null;
    private mycost o3 = null;
    private mycost o4 = null;
    private mycost o5 = null;
    private mycost o6 = null;
    private mycost o7 = null;
    private mycost o8 = null;
    private mycost o9 = null;
    private mycost o10 = null;
    private mycost o11 = null;
    private mycost o12 = null;
    private mycost o13 = null;
    private mycost o14 = null;
    private mycost o15 = null;

    public Form2()
    {
        InitializeComponent();

        o1 = new mycost();
        o2 = new mycost();
        o3 = new mycost();
        o4 = new mycost();
        o5 = new mycost();
        o6 = new mycost();
        o7 = new mycost();
        o8 = new mycost();
        o9 = new mycost();
        o10 = new mycost();
        o11 = new mycost();
        o12 = new mycost();
        o13 = new mycost();
        o14 = new mycost();
        o15 = new mycost();

        costList.Add(o1);
        costList.Add(o2);
        costList.Add(o3);
        costList.Add(o4);
        costList.Add(o5);
        costList.Add(o6);
        costList.Add(o7);
        costList.Add(o8);
        costList.Add(o9);
        costList.Add(o11);
        costList.Add(o12);
        costList.Add(o13);
        costList.Add(o14);
        costList.Add(o15);

        FileStream df = new FileStream("comoditys.dat", FileMode.Open);
        BinaryFormatter abf = new BinaryFormatter();
        costList = (List<mycost>)abf.Deserialize(df);
        df.Close();

        if (costList != null)
        {
            if (costList.Count > 0)
                Alligor = costList[0].secondPrice;

            if (costList.Count > 1)
                Briochit = costList[1].secondPrice;

            if (costList.Count > 2)
                Chollonin = costList[2].secondPrice;

            if (costList.Count > 3)
                Espitium = costList[3].secondPrice;

            if (costList.Count > 4)
                Hydrobenol = costList[4].secondPrice;

            if (costList.Count > 5)
                Isopropenetol = costList[5].secondPrice;

            if (costList.Count > 6)
                Metachropin = costList[6].secondPrice;

            if (costList.Count > 7)
                Phlobotil = costList[7].secondPrice;

            if (costList.Count > 8)
                Plasteosine = costList[8].secondPrice;

            if (costList.Count > 9)
                Polynitrocol = costList[9].secondPrice;

            if (costList.Count > 10)
                Polynucleit = costList[10].secondPrice;

            if (costList.Count > 11)
                Prilumium = costList[11].secondPrice;

            if (costList.Count > 12)
                Statchanol = costList[12].secondPrice;

            if (costList.Count > 13)
                Titanium = costList[13].secondPrice;

            if (costList.Count > 14)
                Vitricyl = costList[14].secondPrice;

        }

    }

    private void textBox1_TextChanged(object sender, EventArgs e)
    {
        // 1st text box input is float
        float tempFloat;



        if (float.TryParse(textBox1.Text, out tempFloat))
        {

            AlligorInput = tempFloat;

        }
        else
            MessageBox.Show("uh oh");



    }

    private void textBox2_TextChanged(object sender, EventArgs e)
    {
        // 1st text box input is float
        float tempFloat;



        if (float.TryParse(textBox1.Text, out tempFloat))
        {

            BriochitInput = tempFloat;

        }
        else
            MessageBox.Show("uh oh");



    }

    private void textBox3_TextChanged(object sender, EventArgs e)
    {
        // 1st text box input is float
        float tempFloat;



        if (float.TryParse(textBox1.Text, out tempFloat))
        {

            CholloninInput = tempFloat;

        }
        else
            MessageBox.Show("uh oh");



    }

    private void textBox4_TextChanged(object sender, EventArgs e)
    {
        // 1st text box input is float
        float tempFloat;



        if (float.TryParse(textBox1.Text, out tempFloat))
        {

            EspitiumInput = tempFloat;

        }
        else
            MessageBox.Show("uh oh");



    }

    private void textBox5_TextChanged(object sender, EventArgs e)
    {
        // 1st text box input is float
        float tempFloat;



        if (float.TryParse(textBox1.Text, out tempFloat))
        {

            HydrobenolInput = tempFloat;

        }
        else
            MessageBox.Show("uh oh");



    }

    private void textBox6_TextChanged(object sender, EventArgs e)
    {
        // 1st text box input is float
        float tempFloat;



        if (float.TryParse(textBox1.Text, out tempFloat))
        {

           IsopropenetolInput = tempFloat;

        }
        else
            MessageBox.Show("uh oh");



    }

    private void textBox7_TextChanged(object sender, EventArgs e)
    {
        // 1st text box input is float
        float tempFloat;



        if (float.TryParse(textBox1.Text, out tempFloat))
        {

            MetachropinInput = tempFloat;

        }
        else
            MessageBox.Show("uh oh");



    }

    private void textBox8_TextChanged(object sender, EventArgs e)
    {
        // 1st text box input is float
        float tempFloat;



        if (float.TryParse(textBox1.Text, out tempFloat))
        {

            PhlobotilInput = tempFloat;

        }
        else
            MessageBox.Show("uh oh");



    }

    private void textBox9_TextChanged(object sender, EventArgs e)
    {
        // 1st text box input is float
        float tempFloat;



        if (float.TryParse(textBox1.Text, out tempFloat))
        {

            PlasteosineInput = tempFloat;

        }
        else
            MessageBox.Show("uh oh");



    }

    private void textBox10_TextChanged(object sender, EventArgs e)
    {
        // 1st text box input is float
        float tempFloat;



        if (float.TryParse(textBox1.Text, out tempFloat))
        {

            PolynitrocolInput = tempFloat;

        }
        else
            MessageBox.Show("uh oh");



    }

    private void textBox11_TextChanged(object sender, EventArgs e)
    {
        // 1st text box input is float
        float tempFloat;



        if (float.TryParse(textBox1.Text, out tempFloat))
        {

           PolynucleitInput = tempFloat;

        }
        else
            MessageBox.Show("uh oh");



    }

    private void textBox12_TextChanged(object sender, EventArgs e)
    {
        // 1st text box input is float
        float tempFloat;



        if (float.TryParse(textBox1.Text, out tempFloat))
        {

            PrilumiumInput = tempFloat;

        }
        else
            MessageBox.Show("uh oh");



    }

    private void textBox13_TextChanged(object sender, EventArgs e)
    {
        // 1st text box input is float
        float tempFloat;



        if (float.TryParse(textBox1.Text, out tempFloat))
        {

            StatchanolInput = tempFloat;

        }
        else
            MessageBox.Show("uh oh");



    }

    private void textBox14_TextChanged(object sender, EventArgs e)
    {
        // 1st text box input is float
        float tempFloat;



        if (float.TryParse(textBox1.Text, out tempFloat))
        {

           TitaniumInput = tempFloat;

        }
        else
            MessageBox.Show("uh oh");



    }

    private void textBox15_TextChanged(object sender, EventArgs e)
    {
        // 1st text box input is float
        float tempFloat;



        if (float.TryParse(textBox1.Text, out tempFloat))
        {

           VitricylInput = tempFloat;

        }
        else
            MessageBox.Show("uh oh");



    }

    private void button1_Click(object sender, EventArgs e)
    {
        costofAlligor = Alligor * AlligorInput;
        costofBriochit = Briochit * BriochitInput;
        costofChollonin = Chollonin * CholloninInput;
        costofEspitium = Espitium * EspitiumInput;
        costofHydrobenol = Hydrobenol * HydrobenolInput;
        costofIsopropenetol = Isopropenetol * IsopropenetolInput;
        costofMetachropin = Metachropin * MetachropinInput;
        costofPhlobotil = Phlobotil * PhlobotilInput;
        costofPlasteosine = Plasteosine * PlasteosineInput;
        costofPolynitrocol = Polynitrocol * PolynitrocolInput;
        costofPolynucleit = Polynucleit * PolynucleitInput;
        costofPrilumium = Prilumium * PrilumiumInput;
        costofStatchanol = Statchanol * StatchanolInput;
        costofTitanium = Titanium * TitaniumInput;
        costofVitricyl = Vitricyl * VitricylInput;

        totalCost = costofAlligor + costofBriochit + costofChollonin + costofEspitium + costofHydrobenol + costofIsopropenetol + costofMetachropin + costofPhlobotil + costofPlasteosine + costofPolynitrocol + costofPolynucleit + costofPrilumium + costofStatchanol + costofTitanium + costofVitricyl;

    }

    private void textBox16_TextChanged(object sender, EventArgs e)
    {
         textBox13.Text = totalCost.ToString();

        }
    }
  }

form1 can be found here .

Answer 1

    FileStream df = new FileStream("comoditys.dat", FileMode.Open);
    BinaryFormatter abf = new BinaryFormatter();
    costList = (List<mycost>)abf.Deserialize(df);

it looks like you are opening the comoditiys.dat and it deserializes to List<comoditys> but you are casting them incorrectly to List<mycost> .

EDIT:

Try this

List<comodity> comodities = (List<comodity>)abf.Deserialize(df);
costList = comodities.Select(c => new mycost{secondPrice = c.comodityCost}).ToList();

Answer 2

On the face of it comoditys.dat contains a serialised List<comoditys> and you are trying to cast the deserialised result to a List<mycost>

EDIT

Linq example as per comment, i don't know how a comoditys object maps to a mycost object so property names are just examples.

MyComoditysList.Select(x => new mycost()
{
    myCostProp1 = comoditysProp1,
    myCostProp2 = comoditysProp2,
    myCostProp3 = comoditysProp3
}).ToList();

Answer 3

I'm making a guess here:

What does abf.Deserialize(df) return?

Does it return List<mycost> or something else?

Answer 4

It looks like you are trying to cast a list of comoditys to a list of mycost . You can't do that. It's difficult to provide any other assistance given the size of your code. You should try to minimize it to the smallest reproduction of the error you're experiencing.