无效操作异常未处理（附加信息：Fill：SelectCommand.Connection属性尚未初始化。）

Question

 namespace WindowsFormsApplication5
{
 public partial class Form1 : Form
{
    string conn = "Data Source=JUTT;Initial Catalog=product;Integrated Security=True";
    SqlConnection connection;
    SqlCommand command;
    SqlDataAdapter adapt;
    SqlConnection con;
    DataTable dt;
    string prnt;
    string sql = null;
    ReportDocument crystal = new ReportDocument();
    public Form1()
    {
        InitializeComponent();
    }

    private void crystalReportViewer1_Load(object sender, EventArgs e)
    {

    }

    private void Form1_Load(object sender, EventArgs e)
    {
        crystal.Load(@"c:\users\asad\documents\visual studio 2013\Projects\WindowsFormsApplication5\WindowsFormsApplication5\CrystalReport1.rpt");
    }

    private void button1_Click(object sender, EventArgs e)
    {
        adapt = new SqlDataAdapter("select id,pd_name,price from sale where id like '" + textBox1.Text + "%'", con);
        DataSet ds = new DataSet();
        adapt.Fill(ds, "sale");
        CrystalReport1 rpt = new CrystalReport1();
        rpt.SetDataSource(ds);
        crystalReportViewer1.ReportSource = rpt;
        dt = new DataTable();
    }

    private void button2_Click(object sender, EventArgs e)
    {

                adapt = new SqlDataAdapter("select * from sale", con);
                DataSet ds = new DataSet();
                adapt.Fill(ds, "sale");
                CrystalReport1 rpt = new CrystalReport1();
                rpt.SetDataSource(ds);
                crystalReportViewer1.ReportSource = rpt;
                dt = new DataTable();
    }
}
 }

当我点击按钮2时，我得到例外：

  

未处理的类型＆＃39; System.InvalidOperationException＆＃39;   发生在System.Data.dll的rpt.setdatasource

行

Answer 1

在您的代码中，您已声明SqlConnection con;并且从未对其进行初始化，但稍后您会尝试在数据适配器构造函数中使用它：adapt = new SqlDataAdapter(".......", con);

在使用之前初始化连接（使用适当的连接字符串创建它的实例），例如在表单构造函数中：

public Form1()
{
    InitializeComponent();

    con = new SqlConnection(conn);
}