Question

These are my SQL tables CONSTRAINT [FK_regLloji_regModeli] FOREIGN KEY([Shifra_Mod]

当我阅读Combobox中的文章0001结果时，没关系：

当我尝试像0002这样的另一篇文章时，我看到了这个错误：

这是我从数据库中读取数据的代码。我只对Combobox有问题

    private void txtShifra_KeyDown(object sender, KeyEventArgs e)
    {
using (SqlConnection connection = new SqlConnection(connstring))
{
  SqlCommand command1 =
    new SqlCommand("select * from regLloji where Shifra_Lloji = '" + txtShifra.Text + "'", connection);
  connection.Open();

  SqlDataReader read1 = command1.ExecuteReader();

  while (read1.Read())
  {
      txtShifra.Text = (read1["Shifra_Lloji"].ToString());
      txtLloji.Text = (read1["Lloji"].ToString());
      string combobox = (string)(read1["Shifra_Mod"]);
      comboBox1.SelectedValue = combobox;

  }

  read1.Close();
}}

以下是填充ComboBox的代码：

this.comboBox1.DataBindings.Add(
  new System.Windows.Forms.Binding("SelectedValue", 
  this.regModeliBindingSource, "Shifra_Mod", true));
  this.comboBox1.DataSource = this.regModeliBindingSource;
  this.comboBox1.DisplayMember = "Modeli"; this.comboBox1.ValueMember = "Shifra_Mod";

ComboBox的样式设置为DropDownList。

完整的Windows窗体代码：

using System;
using System.Data;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace PROJECT1
{
    public partial class regLlojet : Form
    {
        public string connstring = @"Data Source=tcp:10.0.0.1;Initial Catalog=Database;User ID=user;Password=pass;MultipleActiveResultSets=true;";
        Timer timer1 = new Timer();
        public regLlojet()
        {
            InitializeComponent();
            if (String.IsNullOrEmpty(txtShifra.Text))
            {
                txtLloji.Enabled = false;
                comboBox1.Enabled = false;
                btnKonfirm.Enabled = false;
                btnDelete.Enabled = false;
            }
            timer1.Interval = 2000; //10 sec interval
            timer1.Tick += new EventHandler(Tick); //Tick event


        }
        private void Tick(object sender, EventArgs e)
        {

            lblRuajtja.Text = "";
            timer1.Stop(); //Stop timer after tick once

        }
        protected override bool ProcessDialogKey(Keys keyData)
        {
            if (Form.ModifierKeys == Keys.None && keyData == Keys.Escape)
            {
                this.Close();
                return true;
            }
            return base.ProcessDialogKey(keyData);
        }
        protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
        {
            //Press Key
            if (keyData == Keys.F2)
            {
                Anulo();
            }
            else if (keyData == Keys.F8)
            {
                btnKonfirm.PerformClick();
            }
            return base.ProcessCmdKey(ref msg, keyData);
        }
        public void Anulo()
        {
            //Clean Textbox
            Action<Control.ControlCollection> func = null;

            func = (controls) =>
            {
                foreach (Control control in controls)
                    if (control is TextBox)
                        (control as TextBox).Clear();
                    else
                        func(control.Controls);
                this.comboBox1.Text = null;

            };

            func(Controls);
            txtLloji.Enabled = false;
            comboBox1.Enabled = false;
            btnKonfirm.Enabled = false;
            btnDelete.Enabled = false;
        }
        private void btnKonfirm_Click(object sender, EventArgs e)
        {
            //Create new user
            if (String.IsNullOrEmpty(txtLloji.Text))
            {
                MessageBox.Show("Plotesoni fushen Lloji", "Error", MessageBoxButtons.OK, MessageBoxIcon.Warning);

            }else if (String.IsNullOrEmpty(comboBox1.Text))
            {
                MessageBox.Show("Plotesoni fushen Modeli", "Error", MessageBoxButtons.OK, MessageBoxIcon.Warning);

            }

            else
            {
                SqlConnection con1 = new SqlConnection(connstring);
                SqlCommand cmd1 = new SqlCommand();
                try
                {
                    if (con1.State == ConnectionState.Closed)
                    {
                        con1.Open();
                    }

                    //Insert Data in Elk_KonfigGrp
                    cmd1 = new SqlCommand("sp_Insert_Lloji", con1);
                    cmd1.Parameters.AddWithValue("@Action", "INSERT");
                    cmd1.CommandType = CommandType.StoredProcedure;
                    cmd1.Parameters.AddWithValue("@Shifra_Lloji", txtShifra.Text);
                    cmd1.Parameters.AddWithValue("@Lloji", txtLloji.Text);
                    cmd1.Parameters.AddWithValue("@Shifra_Mod", comboBox1.SelectedValue);
                    int conn = cmd1.ExecuteNonQuery();
                    if (conn == 0)
                    {
                        //Not updated.
                        lblRuajtja.Text = "Lloji i vetures nuk u ruajt.";
                        timer1.Start(); //start timer  
                    }
                    else
                    {
                        //Updated.
                        lblRuajtja.Text = "Lloji i vetures u ruajt me sukses..";
                        timer1.Start(); //start timer  
                    }
                }
                catch (Exception)
                {// do exception handling here

                    lblRuajtja.Text = "Lloji i vetures nuk u ruajt CATCH.";
                    timer1.Start(); //start timer  
                }
                con1.Close();
                Anulo();
            }
        }
        private void btnDelete_Click(object sender, EventArgs e)
        {
            //Delete
            SqlConnection con3 = new SqlConnection(connstring);
            SqlCommand cmd3 = new SqlCommand();

            try
            {
                if (con3.State == ConnectionState.Closed)
                {
                    con3.Open();
                }

                {
                    //Delete Data in Elk_KonfigEdin
                    cmd3 = new SqlCommand("sp_Insert_Lloji", con3);
                    cmd3.CommandType = CommandType.StoredProcedure;
                    cmd3.Parameters.AddWithValue("@Action", "DELETE");
                    cmd3.Parameters.AddWithValue("@Shifra_Lloji", txtShifra.Text);
                    cmd3.Parameters.AddWithValue("@Lloji", txtLloji.Text);
                    cmd3.Parameters.AddWithValue("@Shifra_Mod", comboBox1.SelectedValue);


                    int conn3 = cmd3.ExecuteNonQuery();
                    if (conn3 == 0)
                    {
                        //Not updated.
                        lblRuajtja.Text = "Lloji i vetures nuk eshte fshir.";
                        timer1.Start(); //start timer  
                    }
                    else
                    {
                        //Updated.
                        lblRuajtja.Text = "Lloji i vetures eshte fshir me sukses.";
                        timer1.Start(); //start timer  
                    }
                }
            }

            catch (Exception)
            {// do exception handling here

                lblRuajtja.Text = "Lloji i vetures nuk eshte fshir.";
                timer1.Start(); //start timer  
            }
            con3.Close();
            Anulo();
        }

        private void btnAnulo_Click(object sender, EventArgs e)
        {
            Anulo();
        }

        private void btnDalje_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void txtShifra_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter)

                if (((TextBox)sender).Text.Length < 5)
                {
                    e.SuppressKeyPress = true;
                    string str = "";
                    int addZeroes = 4 - txtShifra.Text.Length;
                    for (int i = 0; i < addZeroes; i++)
                    {
                        str += "0";
                    }
                    string val = txtShifra.Text;
                    txtShifra.Text = "";
                    txtShifra.Text = str + val;
                    txtLloji.Enabled = true;
                    comboBox1.Enabled = true;
                    txtLloji.Focus();
                    if (txtLloji.Enabled == true)
                    {
                        btnKonfirm.Enabled = true;
                        btnDelete.Enabled = true;
                    }
                    else
                    {
                        btnKonfirm.Enabled = false;
                        btnDelete.Enabled = false;
                    }

                }
                else
                {
                    e.SuppressKeyPress = true;
                    txtLloji.Enabled = true;
                    comboBox1.Enabled = true;
                    txtLloji.Focus();
                    if (txtLloji.Enabled == true)
                    {
                        btnKonfirm.Enabled = true;
                        btnDelete.Enabled = true;
                    }
                    else
                    {
                        btnKonfirm.Enabled = false;
                        btnDelete.Enabled = false;
                    }
                }
            using (SqlConnection connection = new SqlConnection(connstring))
            {
                SqlCommand command1 =
                 new SqlCommand("select * from regLloji where Shifra_Lloji = '" + txtShifra.Text + "'", connection);
                connection.Open();

                SqlDataReader read1 = command1.ExecuteReader();


                while (read1.Read())
                {
                    txtShifra.Text = (read1["Shifra_Lloji"].ToString());
                    txtLloji.Text = (read1["Lloji"].ToString());
                    string combobox = (string)(read1["Shifra_Mod"]);
                    comboBox1.SelectedValue = combobox;
                }
                read1.Close();
            }
        }

        private void txtLloji_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter)
            {
                e.SuppressKeyPress = true;
                comboBox1.Focus();
            }
        }
        private void comboBox1_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter)
            {
                e.SuppressKeyPress = true;
                btnKonfirm.Focus();
            }
        }

        private void txtShifra_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar))
            {
                e.Handled = true;
            }
        }

        private void regLlojet_Load(object sender, EventArgs e)
        {
            this.regModeliTableAdapter.Fill(this.modeliVeturesDataSet.regModeli);
            this.comboBox1.Text = null;

        }
    }
}

Answer 1

确定找到了（我想）。问题是组合框上的DataBinding

this.comboBox1.DataBindings.Add(
  new System.Windows.Forms.Binding("SelectedValue", 
  this.regModeliBindingSource, "Shifra_Mod", true));

我很确定为什么当SelectedValue发生变化时，你的BindingSource会出错。

这条线应该做什么？如果您只是删除它，您的程序将运行正常！（着名的遗言： - ））

从文本框值+数据库连接更改comboBox所选项目

1 个答案: