Question

我正在创建一个链接到数据库的程序。在主窗体上，当用户单击按钮“连接到数据库”时，会加载另一个表单以供用户输入登录详细信息（要连接的服务器，用户名和密码）。但是，由于某种原因，连接无法正常工作。给出的错误是＆＃34; Fill：SelectCommand.Connection属性尚未初始化。＆＃34;

到目前为止，这是我的代码：

public void connectDB_Click(object sender, EventArgs e)
    {
        DatabaseConnection dbConn = new DatabaseConnection();

        if (dbConn.ShowDialog() == DialogResult.OK)
        {
            SqlConnectionStringBuilder connection = new SqlConnectionStringBuilder();
            connection.DataSource = DatabaseConnection.dbNameText;
            connection.UserID = DatabaseConnection.usernameText;
            connection.Password = DatabaseConnection.passwordText;

            SqlConnection con = new SqlConnection(connection.ToString());
            using (SqlCommand command = new SqlCommand("Select name FROM sys.databases;"))
            {


                try
                {
                    SqlDataAdapter sda = new SqlDataAdapter();
                    sda.SelectCommand = command;
                    DataTable table = new DataTable();
                    sda.Fill(table);
                    BindingSource source = new BindingSource();

                    source.DataSource = table;
                    dataGridDataBase.DataSource = source;
                    sda.Update(table);

                    this.dataGridDataBase.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.Fill; //showing data onto the data grid view
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message);
                }

            }

        }
    }

以上是大师班中的代码;主要形式。以下是登录表单中的代码。

public partial class DatabaseConnection : Form
{

    public static string dbNameText;
    public static string usernameText;
    public static string passwordText;
    public bool buttonClicked = false;


    public DatabaseConnection()
    {
        InitializeComponent();
        password.PasswordChar = '•';
    }

    public void connectButton_Click(object sender, EventArgs e)
    {
        buttonClicked = true;
        dbNameText = dbName.Text;
        usernameText = username.Text;
        passwordText = password.Text;


    }
}

请提出任何想法，帮助或解决方案？

Answer 1

您必须连接命令：

using (SqlCommand command = new SqlCommand("Select name FROM sys.databases;", con))
{
  ...
}

通过单独的表单C＃连接到数据库

1 个答案: