Question

我从昨天起就开始研究这个问题了，我无法更新我的数据库。有3个表。这是WinForms之一的一段代码。它加载数据并显示但在网格中手动更改后，我通过调用Update或任何事情都会出现错误。

请帮忙，因为我疯了。

    public partial class Form3 : Form
    {
    //instance fields
    private export2Excel export2XLS;
    private DataSet _dataSet;
    private BindingSource _bsrc;
    private OleDbDataAdapter _dAdapter;
    private OleDbCommandBuilder _cBuilder;
    private DataTable _dTable;

    private void button1_Click(object sender, EventArgs e)
    {
        //create the connection string
        string connString = "Provider=Microsoft.Jet.OLEDB.4.0;Data      
        Source='C:\\Documents and Settings\\dorota\\Moje dokumenty\\Visual Studio  
        2010\\Projects\\WindowsFormsApplication1\\WindowsFormsApplication1\\artb.mdb'";

        //create the database query
        string query = "SELECT * FROM Samochody";
        System.Data.DataSet DtSet = new System.Data.DataSet();
        _dataSet = DtSet;
        //create an OleDbDataAdapter to execute the query
        OleDbDataAdapter dAdapter = new OleDbDataAdapter(query, connString);
        dAdapter.FillSchema(_dataSet, SchemaType.Source);

        _dAdapter = dAdapter;
        //create a command builder
        OleDbCommandBuilder cBuilder = new OleDbCommandBuilder(_dAdapter);
        _cBuilder = cBuilder;
        //create a DataTable to hold the query results
        DataTable dTable = new DataTable();
        _dTable = dTable;
        //fill the DataTable
        _dAdapter.Fill(_dTable);
        //_dAdapter.TableMappings.Add("Samochody", "Table");

        _dAdapter.Fill(_dataSet);

        // --------------------- to datagridview !

        //BindingSource to sync DataTable and DataGridView
        BindingSource _bsrc = new BindingSource();

        //set the BindingSource DataSource
        //bSource.DataSource = _dTable;
        _bsrc.DataSource = _dTable;
        //_bsrc = bSource;
        //set the DataGridView DataSource
        dataGridView1.DataSource = _bsrc;
    }
    }

这里......：

    private void sqlsave_Click(object sender, EventArgs e)
    {

        //int i=_dAdapter.Update(_dTable);
        _dAdapter.Update(_dataSet.Tables["Samochody"]);
        //_dAdapter.Update(_dataSet,"Samochody");
    }

// --------------------------------------------- ------------------------------------

确定。我已经改变了这个

的sqlsave方法

    private void sqlsave_Click(object sender, EventArgs e)
    {

    try
    {
        //_dAdapter.Update(_dataSet.Tables["Samochody"]);
         OleDbCommand oldb= _cBuilder.GetUpdateCommand();
         int i=oldb.ExecuteNonQuery();
         System.Windows.Forms.MessageBox.Show(i+" rows affected.");
        //_dAdapter.Update(_dataSet,"Samochody");
    }catch(OleDbException oldbex){
        System.Windows.Forms.MessageBox.Show(oldbex.ToString());
    }

现在我终于得到了比“错误”

更多的信息

类型'System.InvalidOperationException'的未处理异常发生在System.Data.dll中的附加信息：ExecuteNonQuery 需要一个开放且可用的连接。连接的当前国家关闭。

所以，让我改变一下，如果是这样的话，我会告诉你的。

// --------------------------------

没有。没有。太快了，不能持久。现在，在试图保存的时候我再次遇到异常， connectin打开，但是（我无法发布图像）当我调试它时，我看到我的OleDbCommand对象类型为_commandText

“更新Samochody SET Item = ?, Data dyspozycji autem od =？，...”

等等。我想这就是原因。我对吗？怎么办？

Answer 1

您没有为OleDbDataAdapter提供连接。尝试这样的事情：

该示例与您的代码不同，但它显示了New Connection的声明并将其传递给OleDbDataAdapter

        string connetionString = null;
        OleDbConnection connection ;
        OleDbDataAdapter oledbAdapter ;
        OleDbCommandBuilder oledbCmdBuilder ;
        DataSet ds = new DataSet();
        int i = 0;
        string sql = null;
        connetionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=Your mdb filename;";
        connection = new OleDbConnection(connetionString);
        sql = "select * from tblUsers";
        try
        {
            connection.Open();  // your code must have like this
            oledbAdapter = new OleDbDataAdapter(sql, connection);
            oledbCmdBuilder = new OleDbCommandBuilder(oledbAdapter);
            oledbAdapter.Fill(ds);
            for (i = 0; i <= ds.Tables[0].Rows.Count - 1; i++)
            {
                ds.Tables[0].Rows[i].ItemArray[2] = "neweamil@email.com";
            }
            oledbAdapter.Update(ds.Tables[0]);
            connection.Close();
            MessageBox.Show ("Email address updates !");
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.ToString());
        }

Answer 2

我找到了答案：

但更好的方法是使用拖放功能并从代码中学习。

Select Data|View Datasources. Your dataset should be visible in the DataSources Window.
Drag a table to a (new) form. VS2005 will add a load of components and a few lines of code.

表单现在将有一个数据集实例，这是Adapter.Fill和.Update方法的参考点。

简单而且效果很好！：D
我在这里找到了它：https://stackoverflow.com/a/548124/1141471

OleDbDataAdapter：无法更新数据库

2 个答案: