c# - 从组合框和文本框中搜索数据。如何在executenotquery()之后将数据加载到datagridview中

Question

现在我有一个组合框，我选择“名称”并输入一些文本。我从数据库中查询数据。但现在我不知道如何将数据加载到datagridview中。这是我的代码按钮搜索:

private void btnSearch_Click(object sender, EventArgs e)
        {
            String strSearch = txtSearch.Text.Trim();
            String Selected = cbSearch.GetItemText(cbSearch.SelectedItem);
            switch (Selected)
            {
                case "All Search":
                    LoadData();
                    break;
                case "Name":
                    try
                    {
                        if (conn.State == ConnectionState.Open)
                            conn.Close();
                        MySqlCommand cmd = new MySqlCommand("Select * FROM sinhvien where name LIKE @name");
                        cmd.Connection = conn;
                        cmd.Connection.Open();
                        cmd.Parameters.Add(new MySqlParameter("@name", "%" + txtSearch.Text + "%"));
                        cmd.ExecuteNonQuery();***//I dont't know what to do after query here***
                        MessageBox.Show("Delete this row successfully!\n",
                            "Notification", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    }
                    catch (MySqlException)
                    {
                        MessageBox.Show("Error load data from database!","Notification", MessageBoxButtons.OK,
                            MessageBoxIcon.Error);
                    }
                    break;
                    break;
            }
        }

然后如何将数据从数据库加载到datagridview中:

private void LoadData()
        {
            try
            {
                conn = new MySqlConnection(connString);
                if (conn.State == ConnectionState.Open)
                    conn.Close();
                daSinhVien = new MySqlDataAdapter("SELECT * FROM sinhvien", conn);
                dtSinhVien = new DataTable();
                dtSinhVien.Clear();
                daSinhVien.Fill(dtSinhVien);
                dgvSinhVien.DataSource = dtSinhVien;
            }
            catch (MySqlException)
            {
                MessageBox.Show("Can't not load data from sinhvien!!","Notification",MessageBoxButtons.OK,
                    MessageBoxIcon.Error);
            }
            cbSearch.Items.Add("All Search");
            cbSearch.Items.Add("Name");
            cbSearch.Items.Add("Age");
            cbSearch.Items.Add("Class");
            cbSearch.Items.Add("Address");
        }

Answer 1

为什么使用 cmd.ExecuteNonQuery();？

这用于执行您不希望返回数据的语句 - 例如调整某些记录的命令。

相反，您可能正在寻找类似的内容:

SqlConnection sqlConnection1 = new SqlConnection("Your Connection String");
SqlCommand cmd = new SqlCommand();
SqlDataReader reader;

cmd.CommandText = "SELECT * FROM Customers";
cmd.CommandType = CommandType.Text;
cmd.Connection = sqlConnection1;

sqlConnection1.Open();

reader = cmd.ExecuteReader();
// Data is accessible through the DataReader object here.

sqlConnection1.Close();

...这是 MSDN 页面之外的内容:https://msdn.microsoft.com/en-us/library/fksx3b4f.aspx