程序错误：无效的对象名System.Data.DataRowView [英] Programm Error: Invalid Objectname System.Data.DataRowView

问题描述

你好我已经尝试了很多可能但我没有得到它：

我有两个组合框和一个按钮。我想首先从每个组合框中选择并显示Form2中的记录（datagridview）

 公开 部分 类 Form1：表格
 {
 
  private   void  button1_Click（ object  sender， EventArgs e）
 {
  //  连接字符串 
  string  C = ConfigurationManager.ConnectionStrings [  DB ] .ConnectionString; 
 SqlConnection con =  new  SqlConnection（C）; 
 SqlCommand cmd =  new  SqlCommand（）; 
 cmd.Connection = con; 
 
  //  撰写查询 
 Form2 f2 =  new  Form2（）; 
  string  qry =  ; 
  string  qrynew =  选择 + cbNr.SelectedItem +   from + cbTbl.SelectedItem +   [DBN Zeichen] ='AB'; 
 
  if （cbTbl.SelectedItem！=  null && cbEIU。 SelectedItem！=  null ）
 {
  this  .Hide（）; 
 f2.copyfun（qrynew）; 
 f2.show（）; 
} 
  else  
 {
 MessageBox.Show（ 错误首先选择一个tbl）; 
} 
} 
} 
} 

Form2：

  public   partial  < span class =code-keyword> class  Form2：表格
 {
  public  Standardbericht（）
 {
 InitializeComponent（）; 
} 
 
 DataTable dt; 
 
  private   void  Standardbericht_Load（对象发​​件人，EventArgs e）
 {
  //   lbTblname.Text = cbTbl .Text;  
  string  C = ConfigurationManager.ConnectionStrings [  DB]的ConnectionString。 
 SqlConnection con =  new  SqlConnection（C）; 
 SqlCommand cmd =  new  SqlCommand（）; 
 cmd.Connection = con; 
 
} 
  //  从上一页获取/检索记录 
  private   void  loadgrid（ string  qrynew）
 {
  string  C = ConfigurationManager.ConnectionStrings [ < span class =code-string> DB]。ConnectionString; 
 SqlConnection con =  new  SqlConnection（C）; 
 SqlCommand cmd =  new  SqlCommand（）; 
 cmd.Connection = con; 
 cmd.CommandText =（qrynew）; 
 DataSet d =  new  DataSet（）; 
  //   dt = new DataTable（）;  
 SqlDataAdapter da =  new  SqlDataAdapter（cmd）; 
  da.Fill（d）;  
 dgvSbericht.DataSource = d; 
  //   dgvSbericht.DataSource = d.Tables [0];  
 
} 
 
  public   void  copyfun（ string  qrynew）
 {
 loadgrid（qrynew）; 
} 
} 
} 

我的查询

 string qrynew =   SELECT + cbNr .SelectedItem +   from + cbTbl.SelectedItem +    [DBN Zeichen] ='AB'; 
 

如果我在线调试它就是我得到的（cmd.CommandText =（qrynew）：

Quote：

从System.Data.DataRowView中选择16，其中[DBN Zeichen] =' AB'

解决方案

cbTbl.SelectedItem是DataRowView，所以你需要得到如下的值

 cbTbl.SelectedItem.Row [  ColumnName]。ToString（）

以及 cbNr.SelectedItem 给你的值为 16 可能是你想要 cbNr.SelectedItem.Text 或 cbNr.SelectedItem.Value 取决于你如何完成数据绑定。

这种连接sql字符串的方式对于sql注入攻击都是开放的。你最好总是尝试使用参数化查询

有很多强度我终于解决了.Bravo

  public   partial   class  Form1：表格
 {
 
  private  < span class =code-keyword> void  button1_Click（ object  sender，EventArgs e）
 {
  //  连接字符串 
 字符串 C = ConfigurationManager。 ConnectionStrings [  DB]。ConnectionString; 
 SqlConnection con =  new  SqlConnection（C）; 
 SqlCommand cmd =  new  SqlCommand（）; 
 cmd.Connection = con; 
 cmd.CommandText =（  sp）; 
 cmd.CommandType = CommandType.StoredProcedure; 
 cmd.Parameters.AddWithValue（  @ table_name，cbTbl.SelectedValue）; 
 
 
  //  撰写查询 
 Form2 f2 =  new  Form2（）; 
  string  qry =  ; 
  string  qrynew = cmd.CommandText 
 
  if （cbTbl。 SelectedItem！=  null && cbNr.SelectedItem！=  null ）
 {
  this  .Hide（）; 
 f2.copyfun（qrynew）; 
 f2.show（）; 
} 
  else  
 {
 MessageBox.Show（ 错误首先选择一个tbl）; 
} 
} 
} 
} 

Hallo i've tried many posibilities but i ain't getting it:
I have two comboboxes and a button. i wanna first choose from each combobox and dispaly the records in Form2 (datagridview)

public partial class Form1 : Form
    {
       
private void button1_Click(object sender, EventArgs e)
        {
            //Connection string
            string C = ConfigurationManager.ConnectionStrings["DB"].ConnectionString;
            SqlConnection con = new SqlConnection(C);
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;

            //write a query
            Form2 f2 = new Form2();
            string qry = "";
            string qrynew = " select " + cbNr.SelectedItem  + " from " + cbTbl.SelectedItem + " where [DBN Zeichen] = 'AB' ";
            
            if (cbTbl.SelectedItem != null && cbEIU.SelectedItem != null)
            {
                    this.Hide();
                    f2.copyfun(qrynew);       
                    f2.show();
                }
                else
                {
                    MessageBox.Show ("ERROR First choose a tbl");
                }
            }
        }
    }

Form2:

     public partial class Form2 : Form
    {
        public Standardbericht()
        {
            InitializeComponent();
        }

        DataTable dt;

        private void Standardbericht_Load(object sender, EventArgs e)
        {
            //lbTblname.Text = cbTbl.Text;
            string C = ConfigurationManager.ConnectionStrings["DB"].ConnectionString;
            SqlConnection con = new SqlConnection(C);
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;

        }
        // Get/ retrieve records from the previous page
        private void loadgrid(string qrynew)
        {
            string C = ConfigurationManager.ConnectionStrings["DB"].ConnectionString;
            SqlConnection con = new SqlConnection(C);
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandText = (qrynew);
            DataSet d = new DataSet();
            //dt = new DataTable();
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            da.Fill(d);
            dgvSbericht.DataSource = d;
            //dgvSbericht.DataSource = d.Tables[0];

        }

        public void copyfun(string qrynew)
        {
            loadgrid(qrynew);
        }
    }
}

My Query

string qrynew = "SELECT " + cbNr.SelectedItem  + " from " + cbTbl.SelectedItem + " where [DBN Zeichen] = 'AB'";

And that's what i get if i debug it on line (cmd.CommandText = (qrynew):

Quote:

select 16 from System.Data.DataRowView where [DBN Zeichen] = 'AB'

解决方案

cbTbl.SelectedItem is DataRowView, so you need to get the value as below

cbTbl.SelectedItem.Row["ColumnName"].ToString()

and also cbNr.SelectedItem giving you value as 16 may be you want cbNr.SelectedItem.Text or cbNr.SelectedItem.Value depending on how you done the data binding.
any way this way of concatenating sql string is open for sql injection attacks. you better always try to use parameterized query

With a lot of intensity i finally solved it. Bravo

public partial class Form1 : Form
    {
       
private void button1_Click(object sender, EventArgs e)
        {
            //Connection string
            string C = ConfigurationManager.ConnectionStrings["DB"].ConnectionString;
            SqlConnection con = new SqlConnection(C);
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandText = ("sp");
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.AddWithValue("@table_name", cbTbl.SelectedValue);

 
            //write a query
            Form2 f2 = new Form2();
            string qry = "";
            string qrynew = cmd.CommandText
            
            if (cbTbl.SelectedItem != null && cbNr.SelectedItem != null)
            {
                    this.Hide();
                    f2.copyfun(qrynew);       
                    f2.show();
                }
                else
                {
                    MessageBox.Show ("ERROR First choose a tbl");
                }
            }
        }
    }

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