OledbException - 字段太小而无法接受数据量

Question

我正在尝试使用 OleDb 通过 SQL 命令将新记录插入到名为 'tblThread' 的实体（包含讨论帖子，如果您想知道的话）中；这是通过一个按钮完成的，该按钮将从两个控件（都是文本框）中获取值。

这里是布局，如果你想看：https://gyazo.com/c43abf4ce055ff997b908badb57f549a 但是，在单击按钮 'Submit Discussion' 后，插入新记录的控件出现错误显示：

https://gyazo.com/1dbdb33290649af04f092533560b1d8c

下面是这个按钮的 Click 事件的代码：

请注意：

absDefault._memberType = 'Teacher'（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());
    }
}

我猜问题出在属性 [Description] 上，不过，我已将数据类型设置为长文本： https://gyazo.com/2d99c945a0a0b98a1e48e8abaf043c2f

如果您想知道我的数据库连接中包含什么 class： http://pastebin.com/RQs6qPEz

让我感到困惑的是，我的输入是在边界内的（少于 255 个字符，如果这是问题所在）：例如，https://gyazo.com/c43abf4ce055ff997b908badb57f549a 如您所见，除了标签 'Description' 之外的 'masked textbox' 包含小于 255 个字符的值。

我已经尝试调试以找到solution/answer。

Answer 1

System.Data.OleDb 允许我们对参数（及其占位符）使用@names，但它忽略名称并将参数视为严格的位置。因此必须按照它们在命令文本中出现的相同顺序声明参数。

在您指定的命令文本中

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

但是当您通过 AddWithValue 创建参数时，您会按以下顺序创建参数...

@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数据量

OledbException - Field too small to accept amount of data

c#

oledb

ms-access