C＃编码在mysql中获取数据 [英] C# coding to obtain the data in mysql

问题描述

hai

i我是一名从事msql数据库获取数据项目的学生，我试着在c＃中为windows应用程序编写代码，但是我收到了一些错误，所以请帮助我有这些错误



代码是

hai
i am a student working on the project of obtaining the data fro the msql database,i tried to write the code in c# for windows application but i receive some errors in that so please help me with those errors

code is

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.Data.SqlClient;

namespace WindowsFormsApplication9
{
    public partial class Form1 : Form
    {
        //SqlConnection con = new SqlConnection( "server=localhost;user id=root;password=******;database=test");//
        SqlConnection con = new SqlConnection();

        public Form1()
        {
            InitializeComponent();
        }


        private void button1_Click(object sender, EventArgs e)
        {
            try
            {
               // con.ConnectionString = "server=localhost;user id=root;password=*****;database=test";

                con.ConnectionString = "server=.\\sqlexpress;database=test;integrated security=true;";

                SqlDataAdapter adp = new SqlDataAdapter("SELECT Date_time,CT1_AH,CT2_AH,CT3_AH,CT1_WattHr,CT2_WattHr,Max_Temperature,Min_Temperature,Volt1,Amp1,Volt2,Batt1_percentFull,Batt1_gotcharged,Batt2_percentFull,Batt2_gotcharged FROM periodicdata WHERE Date_time BETWEEN '" + dateTimePicker1.Value.ToShortDateString() + "' AND '" + dateTimePicker2.Value.ToShortDateString() + "'", con);
                DataSet ds = new DataSet();
                adp.Fill(ds, "s");
                if (ds.Tables["s"].Rows.Count > 0)
                {
                    for (int i = 0; i < ds.Tables["s"].Rows.Count; i++)
                    {
                        dataGridView1.Rows.Add();
                        dataGridView1.Rows[i].Cells[0].Value = ds.Tables["s"].Rows[i].ItemArray[0];
                        dataGridView1.Rows[i].Cells[1].Value = ds.Tables["s"].Rows[i].ItemArray[1];
                        dataGridView1.Rows[i].Cells[2].Value = ds.Tables["s"].Rows[i].ItemArray[2];
                        dataGridView1.Rows[i].Cells[3].Value = ds.Tables["s"].Rows[i].ItemArray[3];
                        dataGridView1.Rows[i].Cells[4].Value = ds.Tables["s"].Rows[i].ItemArray[4];
                        dataGridView1.Rows[i].Cells[5].Value = ds.Tables["s"].Rows[i].ItemArray[5];
                        dataGridView1.Rows[i].Cells[6].Value = ds.Tables["s"].Rows[i].ItemArray[6];
                        dataGridView1.Rows[i].Cells[7].Value = ds.Tables["s"].Rows[i].ItemArray[7];
                        dataGridView1.Rows[i].Cells[8].Value = ds.Tables["s"].Rows[i].ItemArray[8];
                        dataGridView1.Rows[i].Cells[9].Value = ds.Tables["s"].Rows[i].ItemArray[9];
                        dataGridView1.Rows[i].Cells[10].Value = ds.Tables["s"].Rows[i].ItemArray[10];
                        dataGridView1.Rows[i].Cells[11].Value = ds.Tables["s"].Rows[i].ItemArray[11];
                        dataGridView1.Rows[i].Cells[12].Value = ds.Tables["s"].Rows[i].ItemArray[12];
                        dataGridView1.Rows[i].Cells[13].Value = ds.Tables["s"].Rows[i].ItemArray[13];
                        dataGridView1.Rows[i].Cells[14].Value = ds.Tables["s"].Rows[i].ItemArray[14];
                    }
                }
                else
                {
                    MessageBox.Show("No Record Found For Given Date.");
                }
            }
            catch (Exception ex) { MessageBox.Show(ex.ToString()); }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            dataGridView1.Columns.Add("", "Date Time");
            dataGridView1.Columns.Add("", "CT1_AH");
            dataGridView1.Columns.Add("", "CT2_AH");
            dataGridView1.Columns.Add("", "CT3_AH");
            dataGridView1.Columns.Add("", "CT1_WattHr");
            dataGridView1.Columns.Add("", "CT2_WattHr");
            dataGridView1.Columns.Add("", "Max_Temperature");
            dataGridView1.Columns.Add("", "Min_Temperature");
            dataGridView1.Columns.Add("", "Volt1");
            dataGridView1.Columns.Add("", "Amp1");
            dataGridView1.Columns.Add("", "Volt2");
            dataGridView1.Columns.Add("", "Batt1_percentFull");
            dataGridView1.Columns.Add("", "Batt1_gotCharged");
            dataGridView1.Columns.Add("", "Batt2_percentFull");
            dataGridView1.Columns.Add("", "Batt2_gotCharged");

            ChangeDateFormat(dateTimePicker1);
            ChangeDateFormat(dateTimePicker2);
        }

        public void ChangeDateFormat(DateTimePicker dtp)
        {
            dtp.Format = DateTimePickerFormat.Custom;
            dtp.CustomFormat = "MM/dd/yyyy";
        }

        private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {

        }

    }
}

我收到的错误是

and the error i receive is

system.InvalidOperationException: The ConnectionString property has not been initialized.
at System.Data.SqlClient.SqlConnectionFactory.PermissionDemand()
at
System.Data.SqlClient.SqlConnectionFactory.permissionDemand(DbConnectionouterConnection)
at
System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnectionouterConnection,DbConnectionFactory connectionFactory)
at System.Data.SqlClient.SqlConnection.Open()
at WindowsFormsApplication9.Form1.button1_Click(Object sender, EventArgse) in
D:\WindowsFormsApplication9\Form1.cs:line29

推荐答案

您没有在连接上调用Open，因此它未打开。将来，如果您希望我们告诉您它的含义，请给我们错误信息。

You have not called Open on the connection, so it is not open. In future, give us the error message if you want us to tell you what it means.

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