System.InvalidCastException：'指定的强制转换无效。' [英] System.InvalidCastException: 'Specified cast is not valid.'
问题描述
您好我在2017年Visual Studio社区中创建了一个IT库应用程序，代码在asp.net / C＃中。当我将数据提交到SQL表时，我收到此错误
Hi i am creating a IT Inventory application in visual studio community 2017 , the code is in asp.net / C#. When i submit the data to the SQL table i received this error
System.InvalidCastException：'指定的强制转换无效。'
我的sql表查询是：
CREATE TABLE [dbo]。[工作站]（
[Emp_Id] [int] IDENTITY（1,1）NOT NULL，
[Emp_Name] [varchar]（30）NOT NULL，
[Emp_Surname] [varchar]（30）NOT NULL，
[部门] [varchar]（50）NOT NULL，
[Company] [varchar]（30）NOT NULL，
[Hostname] [ nvarchar]（20）NOT NULL，
[Wkst_Status] [varchar]（15）NOT NULL，
[Make] [varchar]（12）NOT NULL，
[型号] [varchar]（15）NOT NUL L，
[SerialNumber] [nvarchar]（30）NOT NULL，
[ProductNumber] [nvarchar]（30）NOT NULL，
[Purch_Date ] [date] NOT NULL，
[WExpiry_Date] [date] NOT NULL，
[Memory] [nvarchar]（6）NOT NULL，
[Processor] [nvarchar]（10）NOT NULL，
[HDD] [nvarchar]（10）NOT NULL，
[OS] [nvarchar]（25）NOT NULL，
CONSTRAINT [PK__Workstat__262359ABF6F5A9AA] PRIMARY KEY CLUSTERED
（
[Emp_Id] ASC
）WITH（ PAD_INDEX = OFF，STATISTICS_NORECOMPUTE = OFF，IGNORE_DUP_KEY = OFF，ALLOW_ROW_LOCKS = ON，ALLOW_PAGE_LOCKS = ON）ON [PRIMARY]
）ON [PRIMARY]
GO
CREATE TABLE [dbo].[Workstations](
[Emp_Id] [int] IDENTITY(1,1) NOT NULL,
[Emp_Name] [varchar](30) NOT NULL,
[Emp_Surname] [varchar](30) NOT NULL,
[Department] [varchar](50) NOT NULL,
[Company] [varchar](30) NOT NULL,
[Hostname] [nvarchar](20) NOT NULL,
[Wkst_Status] [varchar](15) NOT NULL,
[Make] [varchar](12) NOT NULL,
[Model] [varchar](15) NOT NULL,
[SerialNumber] [nvarchar](30) NOT NULL,
[ProductNumber] [nvarchar](30) NOT NULL,
[Purch_Date] [date] NOT NULL,
[WExpiry_Date] [date] NOT NULL,
[Memory] [nvarchar](6) NOT NULL,
[Processor] [nvarchar](10) NOT NULL,
[HDD] [nvarchar](10) NOT NULL,
[OS] [nvarchar](25) NOT NULL,
CONSTRAINT [PK__Workstat__262359ABF6F5A9AA] PRIMARY KEY CLUSTERED
(
[Emp_Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
我的C＃代码 ，错误出现在 if（（bool）item [" Wkst_Status"]）
使用System;
使用System.Collections.Generic;
使用System.ComponentModel;
使用System.Data ;
使用System.Data.SqlClient;
使用System.Drawing;
使用System.Linq;
使用System.Text;
$
使用System.Threading.Tasks;
使用System.Windows.Forms;
使用System.Configuration;
$
$ b命名空间库存数据库$
{
;  公共部分班级工作站：表格
  {
&NBSP; &NBSP; &NBSP;私有IEnumerable< object>查询;
&NBSP; &NBSP; &NBSP;公共对象WExpiry_Date {get;私人集; }
&NBSP; &NBSP; &NBSP;公共工作站（）
&NBSP; &NBSP; &NBSP; {
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; InitializeComponent（）;
&NBSP; &NBSP; &NBSP; }
&NBSP; &NBSP; &NBSP; private void label1_Click（object sender，EventArgs e）
&NBSP; &NBSP; &NBSP; {
$
&NBSP; &NBSP; &NBSP; }
&NBSP; &NBSP; &NBSP; private void label1_Click_1（object sender，EventArgs e）
&NBSP; &NBSP; &NBSP; {
$
&NBSP; &NBSP; &NBSP; }
&NBSP; &NBSP; &NBSP; private void Workstations_Load（object sender，EventArgs e）
&NBSP; &NBSP; &NBSP; {
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; // TODO：这行代码将数据加载到'iTInventoryDataSet.Workstations'表中。您可以根据需要移动或移除它。
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; //this.workstationsTableAdapter.Fill(this.iTInventoryDataSet.Workstations）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; comboBox3.SelectedIndex = 0;
&NBSP; &NBSP; &NBSP; }
&NBSP; &NBSP; &NBSP; private void button1_Click（object sender，EventArgs e）
&NBSP; &NBSP; &NBSP; {
$
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; SqlConnection con = new SqlConnection（@"Data Source = sh-jasonk \ dev; Initial Catalog = ITInventory; Integrated Security = True"）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; //插入逻辑
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; con.Open（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; bool Wkst_Status = false;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; if（comboBox3.SelectedIndex == 0）
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; {
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; Wkst_Status = true;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; }¥b $ b &NBSP; &NBSP; &NBSP; &NBSP; &NBSP;否则
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; {
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; Wkst_Status = false;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; }
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; SqlCommand cmd = new SqlCommand
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; （@"INSERT INTO [dbo]。[工作站]
（
&NBSP;&NBSP; [EMP_NAME]
&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP; [Emp_Surname]
&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP ;，[部门]
，[Company]
， [主机名]
&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP; [Wkst_Status]
&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;，[使]¥b $ b ，[Model]
，[SerialNumber] <登记/>
&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP; [ProductNumber]
&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP; [Purch_Date]
&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP; [WExpiry_Date]
&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;，[存储器]
，[Processor]
& NBSP; &NBSP; &NBSP; &NBSP; &NBSP; ，[HDD]
&NBSP; &NBSP; &NBSP; &NBSP; ，[OS]）
&NBSP; VALUES
&NBSP; &NBSP; &NBSP; &NBSP; （'" + txtName.Text +"'，'" + txtSurname.Text +"'，'" + comboBox1.Text +"'，'" + comboBox2.Text +"' ，'" + txtHostName.Text +"'，'"
+ comboBox3.SelectedIndex +"'，'" + txtMake.Text +"'，'" + txtModel.Text +" ;'，'" + txtSN.Text +"'，'" + txtPN.Text +"'，'" + dateTimePicker1.Value.ToString（" yyyy / MM / dd"）
+"'，'" + dateTimePicker1.Value.ToString（" yyyy / MM / dd"）+"'，'" + txtMem.Text +"'，'" + txtProc.Text +" ;'，'" + txtHDD.Text +"'，'" + txtOS.Text +"'）"，con）;
$
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; //此处转换失败
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; cmd.ExecuteNonQuery（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; con.Close（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; //阅读数据
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; SqlDataAdapter sda = new SqlDataAdapter（@" Select [Emp_Name]，[Emp_Surname]，[Department]，[Company]，[Hostname]，[Wkst_Status]，[Make]，[Model]
&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP; [的SerialNumber]，[ProductNumber]，[Purch_Date]，[WExpiry_Date]，[存储器]，[处理器]，[HDD]
&NBSP; ，[OS] From [dbo]。[Workstations]"，con）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; DataTable dt = new DataTable（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; sda.Fill（dt）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows.Clear（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; foreach（dt.Rows中的DataRow项目）
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; {
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; int n = dataGridView1.Rows.Add（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [0] .Value = item [" Emp_Name"]。ToString（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [1] .Value = item [" Emp_Surname"]。ToString（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [2] .Value = item [" Department"]。ToString（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [3] .Value = item [" Company"]。ToString（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [4] .Value = item [" Hostname"]。ToString（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; if（（bool）item [" Wkst_Status"]）
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; {
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [5] .Value =" Active"; $
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; }¥b $ b &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP;否则
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; {
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [5] .Value =" Inactive";
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; }
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [6] .Value = item [" Make"]。ToString（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [7] .Value = item [" Model"]。ToString（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [8] .Value = item [" SerialNumber"]。ToString（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [9] .Value = item [" ProductNumber"]。ToString（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [10] .Value = item [" Purch_Date"]。ToString（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [11] .Value = item [" WExpiry_Date"]。ToString（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [12] .Value = item [" Memory"]。ToString（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [13] .Value = item [" Processor"]。ToString（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [14] .Value = item [" HDD"]。ToString（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; &NBSP; dataGridView1.Rows [n] .Cells [15] .Value = item [" OS"]。ToString（）;
&NBSP; &NBSP; &NBSP; &NBSP; &NBSP; }
&NBSP; &NBSP; &NBSP; }
&NBSP; &NBSP; &NBSP; private void label17_Click（object sender，EventArgs e）
&NBSP; &NBSP; &NBSP; {
$
&NBSP; &NBSP; &NBSP; }¥b $ b &NBSP; }
}
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Configuration;
namespace InventoryStock
{
public partial class Workstations : Form
{
private IEnumerable<object> query;
public object WExpiry_Date { get; private set; }
public Workstations()
{
InitializeComponent();
}
private void label1_Click(object sender, EventArgs e)
{
}
private void label1_Click_1(object sender, EventArgs e)
{
}
private void Workstations_Load(object sender, EventArgs e)
{
// TODO: This line of code loads data into the 'iTInventoryDataSet.Workstations' table. You can move, or remove it, as needed.
//this.workstationsTableAdapter.Fill(this.iTInventoryDataSet.Workstations);
comboBox3.SelectedIndex = 0;
}
private void button1_Click(object sender, EventArgs e)
{
SqlConnection con = new SqlConnection(@"Data Source=sh-jasonk\dev;Initial Catalog=ITInventory;Integrated Security=True");
//Insert Logic
con.Open();
bool Wkst_Status = false;
if (comboBox3.SelectedIndex == 0)
{
Wkst_Status = true;
}
else
{
Wkst_Status = false;
}
SqlCommand cmd = new SqlCommand
(@"INSERT INTO [dbo].[Workstations]
(
[Emp_Name]
,[Emp_Surname]
,[Department]
,[Company]
,[Hostname]
,[Wkst_Status]
,[Make]
,[Model]
,[SerialNumber]
,[ProductNumber]
,[Purch_Date]
,[WExpiry_Date]
,[Memory]
,[Processor]
,[HDD]
,[OS])
VALUES
('" + txtName.Text + "','" + txtSurname.Text + "','" + comboBox1.Text + "','" + comboBox2.Text + "','" + txtHostName.Text + "','"
+ comboBox3.SelectedIndex + "','" + txtMake.Text + "','" + txtModel.Text + "','" + txtSN.Text + "','" + txtPN.Text + "','" + dateTimePicker1.Value.ToString("yyyy/MM/dd")
+ "','" + dateTimePicker1.Value.ToString("yyyy/MM/dd") + "','" + txtMem.Text + "','" + txtProc.Text + "','" + txtHDD.Text + "','" + txtOS.Text + "')",con);
//Conversion failed here
cmd.ExecuteNonQuery();
con.Close();
//Reading Data
SqlDataAdapter sda = new SqlDataAdapter(@"Select [Emp_Name],[Emp_Surname],[Department],[Company],[Hostname],[Wkst_Status],[Make],[Model]
,[SerialNumber],[ProductNumber],[Purch_Date],[WExpiry_Date],[Memory],[Processor],[HDD]
,[OS] From [dbo].[Workstations]", con);
DataTable dt = new DataTable();
sda.Fill(dt);
dataGridView1.Rows.Clear();
foreach (DataRow item in dt.Rows)
{
int n = dataGridView1.Rows.Add();
dataGridView1.Rows[n].Cells[0].Value = item["Emp_Name"].ToString();
dataGridView1.Rows[n].Cells[1].Value = item["Emp_Surname"].ToString();
dataGridView1.Rows[n].Cells[2].Value = item["Department"].ToString();
dataGridView1.Rows[n].Cells[3].Value = item["Company"].ToString();
dataGridView1.Rows[n].Cells[4].Value = item["Hostname"].ToString();
if ((bool)item["Wkst_Status"])
{
dataGridView1.Rows[n].Cells[5].Value = "Active";
}
else
{
dataGridView1.Rows[n].Cells[5].Value = "Inactive";
}
dataGridView1.Rows[n].Cells[6].Value = item["Make"].ToString();
dataGridView1.Rows[n].Cells[7].Value = item["Model"].ToString();
dataGridView1.Rows[n].Cells[8].Value = item["SerialNumber"].ToString();
dataGridView1.Rows[n].Cells[9].Value = item["ProductNumber"].ToString();
dataGridView1.Rows[n].Cells[10].Value = item["Purch_Date"].ToString();
dataGridView1.Rows[n].Cells[11].Value = item["WExpiry_Date"].ToString();
dataGridView1.Rows[n].Cells[12].Value = item["Memory"].ToString();
dataGridView1.Rows[n].Cells[13].Value = item["Processor"].ToString();
dataGridView1.Rows[n].Cells[14].Value = item["HDD"].ToString();
dataGridView1.Rows[n].Cells[15].Value = item["OS"].ToString();
}
}
private void label17_Click(object sender, EventArgs e)
{
}
}
}
我做错了什么，我该如何纠正这个问题
What am i doing wrong and how can i rectify the issue
推荐答案
我不清楚错误发生的位置。 它是否出现在插入物上？ 您有以上评论 cmd.ExecuteNonQuery（）;这表明它在那里被提升。 或者...当你在阅读器的
行上进行强制转换时，它会被提升：（ bool）item [" Wkst_Status"]
在任何一种情况下，我都有一些建议：
1。如果要表示布尔值
1. Store the Wkst_Status as a bit rather than varchar if it is meant to represent a Boolean
2，请将Wkst_Status存储为一个而不是varchar。您对Wkst_Status的值来自组合框的SelectedIndex属性。 我假设组合框中只有两个选项（true / false）和索引0 = false等。 没关系，但你还需要确保选择了一个值，
否则SelectedIndex将等于-1（不能转换为bool）。
2. Your value for Wkst_Status is derived from the SelectedIndex property of a combobox. I assume the combobox only has two options in it (true/false) and index 0 = false, etc. That's OK, but you also need to make sure that a value has been selected, otherwise the SelectedIndex will equal -1 (not castable to bool).
3。您可能希望将insert语句移动到字符串变量，以便您可以调试它并验证insert语句是否反映了有效输入
3. you may want to move the insert statement to a string variable so you can debug it and validate the insert statement is reflecting valid input
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