C#学生成绩增删改查的设计与实现，要有菜单功能。数据取至数据库，如没有则建立相应的学生成绩表。

好的，下面是C#学生成绩增删改查的设计与实现，带有菜单功能，数据取至数据库的代码示例：

首先，我们需要创建一个Windows Form应用程序，并添加一个菜单控件和一个DataGridView控件。然后，在Form_Load事件中，我们需要连接数据库并创建学生成绩表（如果不存在）：

private void Form1_Load(object sender, EventArgs e)
{
    // 连接数据库
    string connectionString = "Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=MyDatabase;Integrated Security=True";
    SqlConnection connection = new SqlConnection(connectionString);
    connection.Open();

    // 创建学生成绩表（如果不存在）
    string sql = "IF OBJECT_ID('dbo.StudentScore', 'U') IS NULL " +
                 "CREATE TABLE dbo.StudentScore " +
                 "(ID INT IDENTITY(1,1) PRIMARY KEY, " +
                 "Name VARCHAR(50) NOT NULL, " +
                 "Score INT NOT NULL)";
    SqlCommand command = new SqlCommand(sql, connection);
    command.ExecuteNonQuery();

    connection.Close();
}

接下来，我们需要为菜单控件添加事件处理程序，以便实现学生成绩的增删改查功能。我们将使用SqlCommand和SqlDataAdapter类来执行SQL语句并获取数据：

// 添加学生成绩
private void addToolStripMenuItem_Click(object sender, EventArgs e)
{
    string name = Microsoft.VisualBasic.Interaction.InputBox("请输入学生姓名：", "添加学生成绩");
    int score = int.Parse(Microsoft.VisualBasic.Interaction.InputBox("请输入学生成绩：", "添加学生成绩"));

    string connectionString = "Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=MyDatabase;Integrated Security=True";
    SqlConnection connection = new SqlConnection(connectionString);
    connection.Open();

    string sql = "INSERT INTO dbo.StudentScore (Name, Score) VALUES (@Name, @Score)";
    SqlCommand command = new SqlCommand(sql, connection);
    command.Parameters.AddWithValue("@Name", name);
    command.Parameters.AddWithValue("@Score", score);
    command.ExecuteNonQuery();

    connection.Close();

    MessageBox.Show("学生成绩添加成功！", "添加学生成绩");
    RefreshDataGridView();
}

// 删除学生成绩
private void deleteToolStripMenuItem_Click(object sender, EventArgs e)
{
    int id = int.Parse(Microsoft.VisualBasic.Interaction.InputBox("请输入要删除的学生成绩ID：", "删除学生成绩"));

    string connectionString = "Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=MyDatabase;Integrated Security=True";
    SqlConnection connection = new SqlConnection(connectionString);
    connection.Open();

    string sql = "DELETE FROM dbo.StudentScore WHERE ID = @ID";
    SqlCommand command = new SqlCommand(sql, connection);
    command.Parameters.AddWithValue("@ID", id);
    int rowsAffected = command.ExecuteNonQuery();

    connection.Close();

    if (rowsAffected == 0)
    {
        MessageBox.Show("没有找到对应的学生成绩！", "删除学生成绩");
    }
    else
    {
        MessageBox.Show("学生成绩删除成功！", "删除学生成绩");
        RefreshDataGridView();
    }
}

// 修改学生成绩
private void updateToolStripMenuItem_Click(object sender, EventArgs e)
{
    int id = int.Parse(Microsoft.VisualBasic.Interaction.InputBox("请输入要修改的学生成绩ID：", "修改学生成绩"));
    int score = int.Parse(Microsoft.VisualBasic.Interaction.InputBox("请输入学生成绩：", "修改学生成绩"));

    string connectionString = "Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=MyDatabase;Integrated Security=True";
    SqlConnection connection = new SqlConnection(connectionString);
    connection.Open();

    string sql = "UPDATE dbo.StudentScore SET Score = @Score WHERE ID = @ID";
    SqlCommand command = new SqlCommand(sql, connection);
    command.Parameters.AddWithValue("@Score", score);
    command.Parameters.AddWithValue("@ID", id);
    int rowsAffected = command.ExecuteNonQuery();

    connection.Close();

    if (rowsAffected == 0)
    {
        MessageBox.Show("没有找到对应的学生成绩！", "修改学生成绩");
    }
    else
    {
        MessageBox.Show("学生成绩修改成功！", "修改学生成绩");
        RefreshDataGridView();
    }
}

// 查询学生成绩
private void searchToolStripMenuItem_Click(object sender, EventArgs e)
{
    string name = Microsoft.VisualBasic.Interaction.InputBox("请输入学生姓名：", "查询学生成绩");

    string connectionString = "Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=MyDatabase;Integrated Security=True";
    SqlConnection connection = new SqlConnection(connectionString);
    connection.Open();

    string sql = "SELECT * FROM dbo.StudentScore WHERE Name = @Name";
    SqlCommand command = new SqlCommand(sql, connection);
    command.Parameters.AddWithValue("@Name", name);
    SqlDataAdapter adapter = new SqlDataAdapter(command);
    DataTable dataTable = new DataTable();
    adapter.Fill(dataTable);

    connection.Close();

    if (dataTable.Rows.Count == 0)
    {
        MessageBox.Show("没有找到对应的学生成绩！", "查询学生成绩");
    }
    else
    {
        dataGridView.DataSource = dataTable;
    }
}

// 刷新DataGridView控件中的数据
private void RefreshDataGridView()
{
    string connectionString = "Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=MyDatabase;Integrated Security=True";
    SqlConnection connection = new SqlConnection(connectionString);
    connection.Open();

    string sql = "SELECT * FROM dbo.StudentScore";
    SqlCommand command = new SqlCommand(sql, connection);
    SqlDataAdapter adapter = new SqlDataAdapter(command);
    DataTable dataTable = new DataTable();
    adapter.Fill(dataTable);

    connection.Close();

    dataGridView.DataSource = dataTable;
}

最后，我们需要在菜单控件的Click事件中调用相应的事件处理程序：

private void addToolStripMenuItem_Click(object sender, EventArgs e)
{
    addToolStripMenuItem_Click(sender, e);
}

private void deleteToolStripMenuItem_Click(object sender, EventArgs e)
{
    deleteToolStripMenuItem_Click(sender, e);
}

private void updateToolStripMenuItem_Click(object sender, EventArgs e)
{
    updateToolStripMenuItem_Click(sender, e);
}

private void searchToolStripMenuItem_Click(object sender, EventArgs e)
{
    searchToolStripMenuItem_Click(sender, e);
}

以上就是C#学生成绩增删改查的设计与实现，带有菜单功能，数据取至数据库的代码示例。