Question

我无法找到如何从主键（称为QuestionID）获取整数值并将其显示在标签上。

我认为将此代码放在计时器中可能是个好主意，因为我希望每次添加记录（行）时都要更新它。

我非常感谢任何帮助，因为我有点新手！谢谢！

由于我不知道如何从数据库中获取价值，这是我非常可怜的尝试，因为我不知道如何从数据库中获取价值：

private void timer1_Tick(object sender, EventArgs e)
{
        string connectionString = ConfigurationManager.ConnectionStrings["myconnectionstring"].ConnectionString;
        SqlConnection connect = new SqlConnection(connectionString);
        connect.Open();

        SqlCommand command6 = new SqlCommand("SELECT ([QuestionID]) FROM Questions", connect);

        QuestionNum.Text = 
}

我的其余代码在这里：

private void button1_Click(object sender, EventArgs e)
{
    string connectionString = ConfigurationManager.ConnectionStrings["myconnectionstring"].ConnectionString;

    SqlConnection connect = new SqlConnection(connectionString);
    connect.Open();

    int checkedradiobutton = 0;

    if(radioButton1.Checked)
    {
            checkedradiobutton = 1;
    }
    else if(radioButton2.Checked)
    {
            checkedradiobutton = 2;
    }
    else if(radioButton3.Checked)
    {
            checkedradiobutton = 3;
    }

    string QuestionText = QuestionBox.Text;
    string AnswerText = teacheranswerbox.Text;

    SqlCommand command5 = new SqlCommand(@"INSERT INTO Questions ([Actual answer], [Question Space], [Question Type]) VALUES (@AnswerText, @QuestionText, @checkedradiobutton)", connect);
    command5.Parameters.AddWithValue("@AnswerText", AnswerText);
    command5.Parameters.AddWithValue("@QuestionText", QuestionText);
    command5.Parameters.AddWithValue("@checkedradiobutton", checkedradiobutton);

    command5.ExecuteNonQuery();
}

private void radioButton2_CheckedChanged(object sender, EventArgs e)
{
        if (radioButton2.Checked)
        {
            teacheranswerbox.Text = "You cannot store an answer for a long answer essay question";
            teacheranswerbox.ReadOnly = true;
        }
        else
        {
            teacheranswerbox.ReadOnly = false;
            teacheranswerbox.Text = "Enter the correct answer here";


        }
    }

我试图从中获取数据的表（p.s. QuestionID自动递增）：

CREATE TABLE [dbo].[Questions] 
(
     [QuestionID]     INT           IDENTITY (1, 1) NOT NULL,
     [Actual answer]  NVARCHAR (50) NULL,
     [Question Space] NVARCHAR (50) NULL,
     [Question Type]  INT           NULL,

     PRIMARY KEY CLUSTERED ([QuestionID] ASC)
);

Answer 1

作为您的QuesitionID IDENTITY列，您可以使用像这样的批处理语句返回数据库引擎分配给它的值

string cmdText =@"INSERT INTO Questions 
                  ([Actual answer], [Question Space], [Question Type]) 
                  VALUES (@AnswerText, @QuestionText, @checkedradiobutton);
                  SELECT SCOPE_IDENTITY();"
SqlCommand command5 = new SqlCommand(cmdText, connect);
command5.Parameters.AddWithValue("@AnswerText", AnswerText);
command5.Parameters.AddWithValue("@QuestionText", QuestionText);
command5.Parameters.AddWithValue("@checkedradiobutton", checkedradiobutton);

int result = Convert.ToInt32(command5.ExecuteScalar());
QuestionNum.Text = result.ToString();

SQL Server在同一命令中支持多个语句。用分号分隔它们。在这段代码中，我在第一次INSERT INTO之后添加了对SCOPE_IDENTITY的调用，该调用返回分配给连接相同范围内的IDENTITY字段的最后一个值。应使用ExecuteScalar调用而不是ExecuteNonQuery来检索此值。最后一部分很重要，因为ExecuteNonQuery只告诉您命令添加/修改了多少行，而ExecuteScalar返回执行查询的第一行第一列的值（IE，SCOPE_IDENTITY的值）

Answer 2

您的问题是，您不知道如何获取返回的数据不是吗？

    SqlCommand command6 = new SqlCommand("SELECT ([QuestionID]) FROM Questions", connect);

    String s = "";

    using (SqlDataReader reader = command6.ExecuteReader())
    {
        while (reader.Read())
        {
        for (int i = 0; i < reader.FieldCount; i++)
        {
            s += (reader.GetValue(i));
        }
        }
    }

    QuestionNum.Text = s;

我没有测试过代码，但我认为它应该有用......

似乎无法找到如何从我的表列中取出一个值并将其放在标签C＃上

2 个答案: