Question

我正在尝试使用OleDb将一条新记录插入一个Access数据库，使用SQL命令将一个名为＆＃39; tblThread＆＃39; （包含讨论帖，如果你想知道的话）;这是通过一个按钮来完成的，该按钮将从两个控件（都是文本框）中获取值。

如果您希望查看以下布局：https://gyazo.com/c43abf4ce055ff997b908badb57f549a 但是，点击按钮＆＃39;提交讨论＆＃39;后，插入新记录的控件显示错误：

https://gyazo.com/1dbdb33290649af04f092533560b1d8c

现在，这里是此按钮的Click事件的代码：

请注意：

absDefault._memberType =＆＃39;老师＆＃39; （在这种情况下）

    private void btnCreate_Click(object sender, EventArgs e)
{
    OleDbConnection objConnection = new OleDbConnection(absDefault.conString);
    OleDbCommand objCommand = new OleDbCommand();
    objCommand.Connection = objConnection;

    if (MessageBox.Show("[Piltover]: Are you sure you would like to create this thread", "", MessageBoxButtons.YesNo) == DialogResult.No)
    {
        return; // Does not execute remaining code
    }
    else if (txtTitle.TextLength == 0)
    {
        MessageBox.Show("[Piltover]: You have not created a title");
    }
    else if (mtxtDescription.TextLength == 0)
    {
        MessageBox.Show("[Piltover]: You have not added description to your thread");
    }
    else
    {
        // DBConnection class is only used within this else block and is not needed anywhere else in this form
        DataSet ds; DataRow dRow;
        DatabaseConnection objConnect = new DatabaseConnection(); // Instantiating an object from DBConnectionClass and checking if an identical title exist is much faster than the OLEDB process (shown within try block below)
        objConnect.Connection_String = absDefault.conString;
        objConnect.SQL = "SELECT * FROM tblThread"; ds = objConnect.GetConnection;
        for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
        {
            dRow = ds.Tables[0].Rows[i];
            if (txtTitle.Text.ToUpper() == dRow.ItemArray.GetValue(1).ToString())
            {
                MessageBox.Show("[Piltover]: Thread already exist with the title name given");
                return; 
            }
        }
    }
    // FIX - test to see if it works

    try
    {
        objConnection.Open();

        // Insert new thread record; avoids SQL injection
        objCommand.CommandText = String.Format("INSERT INTO tblThread ([Title], [Description], [ID], [Username], [TeacherBool]) VALUES (@title, @desc, @id, @username, @teacherbool)");//, absDefault.newThreadMemberType);
        objCommand.Parameters.AddWithValue("@title", txtTitle.Text);
        objCommand.Parameters.AddWithValue("@desc", mtxtDescription.Text);
        objCommand.Parameters.AddWithValue("id", absDefault._idNumber);

        if (absDefault._memberType == "Teacher")
        {
            currentTeacher = new csTeacher(absDefault._idNumber, "Teacher");
            objCommand.Parameters.AddWithValue("@teacherbool", "True");
            objCommand.Parameters.AddWithValue("@username", currentTeacher.Username);
        }
        else // else 'Student'
        {
            currentStudent = new csStudent(absDefault._idNumber, "Student");
            objCommand.Parameters.AddWithValue("@teacherbool", "False");
            objCommand.Parameters.AddWithValue("@username", currentStudent.Username);
        }

        objCommand.ExecuteNonQuery();
        MessageBox.Show("[Piltover]: Thread created");

        objConnection.Close();
    }
    catch (Exception Ex)
    {

        MessageBox.Show(Ex.ToString());
    }
}

我猜测问题在于[描述]属性，但是，我已将数据类型设置为长文本： https://gyazo.com/2d99c945a0a0b98a1e48e8abaf043c2f

如果您想知道我的DatabaseConnection类中包含的内容： http://pastebin.com/RQs6qPEz

我感到困惑的是，我的输入是在边界内（如果这是问题，则不超过255个字符）：例如，https://gyazo.com/c43abf4ce055ff997b908badb57f549a 正如您所看到的，“屏蔽”文本框＆＃39;除了标签＆＃39;描述＆＃39;包含少于255个字符的值。

我已尝试调试以尝试找到解决方案/答案。

Answer 1

System.Data.OleDb允许我们将@names用于参数（及其占位符），但忽略名称并将参数视为严格位置。因此，参数必须按照它们在命令文本中出现的顺序声明。

在命令文本中指定

... VALUES (@title, @desc, @id, @username, @teacherbool)

但是当您通过AddWithValue创建参数时，请按以下顺序执行此操作...

@title
@desc
id
@teacherbool
@username

......这是不一样的。

您需要交换在if块中声明@teacherbool和@username参数的顺序。

OledbException - 字段太小而无法接受大量数据

1 个答案: