使用.Contains（）在2D数组中搜索字符串

Question

目前正在建立一个数据库＆＃39;基于2D数组的程序，我目前正在尝试搜索数组以在接受输入之前搜索重复项。我尝试过两种不同的方法，但都会导致同样的错误：

未处理的类型＆＃39; System.NullReferenceException＆＃39;发生在WindowsFormsApplication5.exe

中

附加信息：未将对象引用设置为对象的实例。

1）

stringToCheck = playerIgNameBox.Text;
                foreach (string x in playerArray)
                {
                    if (x.Contains(stringToCheck))
                    {
                        MessageBox.Show("Duplicate Player!", "Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation, MessageBoxDefaultButton.Button1);
                    }
                }

还

2）。

for (int i = 0; i < playerArray.GetUpperBound(0); i++ )
                {
                    for (int j = 0; j < playerArray.GetUpperBound(1); j++)
                    {
                        if (playerArray[i,j].Contains(playerFirstNameBox.Text) && (playerArray[i,j].Contains(playerIgNameBox.Text) && playerArray[i,j].Contains(playerSecondNameBox.Text)))
                        {
                            MessageBox.Show("Player Duplicate!", "Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation, MessageBoxDefaultButton.Button1); //Validation failed, display error message//
                        }
                    }
                }

完整代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication5
{
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        positionLabel.Text = "Current position:" + (currentIndex + 1).ToString() + "/20";
    }

    string[,] playerArray = new string[20, 8]; // Initial player array is declared, this is where the players are stored//
    int currentIndexPlayer = 0;
    int currentIndex = 0;
    string stringToCheck;

    private void addNewPlayerBtn_Click(object sender, EventArgs e)
    { 
        if (addNewPlayerBtn.Text == "Add New Player")
        {
            playerFirstNameBox.ReadOnly = false; //Unlock all fields for input//
            playerIgNameBox.ReadOnly = false;
            playerSecondNameBox.ReadOnly = false;
            contactStreetBox.ReadOnly = false;
            contactTownBox.ReadOnly = false;
            contactPostcodeBox.ReadOnly = false;
            contactEmailBox.ReadOnly = false;
            contactTelephoneBox.ReadOnly = false;

            addNewPlayerBtn.Text = "Confirm"; 
        }
        else if (addNewPlayerBtn.Text == "Confirm")
        {
            if ((playerFirstNameBox.Text != "") && (playerIgNameBox.Text != "") && (playerSecondNameBox.Text != "") && (currentIndexPlayer < 20)) // Validation check to see if all main fields were entered
            {
                for (int i = 0; i < playerArray.GetUpperBound(0); i++ )
                {
                    for (int j = 0; j < playerArray.GetUpperBound(1); j++)
                    {
                        if (playerArray[i,j].Contains(playerFirstNameBox.Text) && (playerArray[i,j].Contains(playerIgNameBox.Text) && playerArray[i,j].Contains(playerSecondNameBox.Text)))
                        {
                            MessageBox.Show("Player Duplicate!", "Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation, MessageBoxDefaultButton.Button1); //Validation failed, display error message//
                        }
                    }
                }

                playerArray[currentIndexPlayer, 0] = playerFirstNameBox.Text;
                playerArray[currentIndexPlayer, 1] = playerIgNameBox.Text;
                playerArray[currentIndexPlayer, 2] = playerSecondNameBox.Text;
                playerArray[currentIndexPlayer, 3] = contactStreetBox.Text;
                playerArray[currentIndexPlayer, 4] = contactTownBox.Text;
                playerArray[currentIndexPlayer, 5] = contactPostcodeBox.Text;
                playerArray[currentIndexPlayer, 6] = contactEmailBox.Text;
                playerArray[currentIndexPlayer, 7] = contactTelephoneBox.Text;

                if (currentIndexPlayer < 20)
                {
                    currentIndexPlayer++;
                }

            }
            else
            {
                if ((playerFirstNameBox.Text != "") && (playerIgNameBox.Text != "") && (playerSecondNameBox.Text != ""))
                {
                    MessageBox.Show("Database full!", "Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation, MessageBoxDefaultButton.Button1); //Validation failed, display error message//
                    addNewPlayerBtn.Text = "Confirm";
                }
                else
                {
                    MessageBox.Show("Fields missing!", "Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation, MessageBoxDefaultButton.Button1); //Validation failed, display error message//
                    addNewPlayerBtn.Text = "Confirm";
                }

            }

            addNewPlayerBtn.Text = "Add New Player";

            playerFirstNameBox.ReadOnly = true; //lock all fields for input again//
            playerIgNameBox.ReadOnly = true;
            playerSecondNameBox.ReadOnly = true;
            contactStreetBox.ReadOnly = true;
            contactTownBox.ReadOnly = true;
            contactPostcodeBox.ReadOnly = true;
            contactEmailBox.ReadOnly = true;
            contactTelephoneBox.ReadOnly = true;

        }
    }

    private void searchToolStripMenuItem_Click(object sender, EventArgs e)
    {
        Form2 searchForm = new Form2();
        searchForm.Show();
    }

    private void showPreviousBtn_Click(object sender, EventArgs e)
    {
        if(currentIndex == 0)
        {
            currentIndex = 19;
        }
        else
        {
            currentIndex--;
        }
        playerFirstNameBox.Text = playerArray[currentIndex, 0];
        playerIgNameBox.Text = playerArray[currentIndex, 1];
        playerSecondNameBox.Text = playerArray[currentIndex, 2];
        contactStreetBox.Text = playerArray[currentIndex, 3];
        contactTownBox.Text = playerArray[currentIndex, 4];
        contactPostcodeBox.Text = playerArray[currentIndex, 5];
        contactEmailBox.Text = playerArray[currentIndex, 6];
        contactTelephoneBox.Text = playerArray[currentIndex, 7];

        positionLabel.Text = "Current position:" + (currentIndex+1).ToString() + "/20";

    }

    private void showNextBtn_Click(object sender, EventArgs e)
    {
        if (currentIndex == 19)
        {
            currentIndex = 0;
        }
        else
        {
            currentIndex++;
        }
        playerFirstNameBox.Text = playerArray[currentIndex, 0];
        playerIgNameBox.Text = playerArray[currentIndex, 1];
        playerSecondNameBox.Text = playerArray[currentIndex, 2];
        contactStreetBox.Text = playerArray[currentIndex, 3];
        contactTownBox.Text = playerArray[currentIndex, 4];
        contactPostcodeBox.Text = playerArray[currentIndex, 5];
        contactEmailBox.Text = playerArray[currentIndex, 6];
        contactTelephoneBox.Text = playerArray[currentIndex, 7];

        positionLabel.Text = "Current position:" + (currentIndex + 1).ToString() + "/20";
    }

}

}