C# 错误：不存在从对象类型System.Data.DataRowView到已知托管提供程序本机类型的映射

你好， 它显示的错误如下……
错误：-不存在从对象类型System.Data.DataRowView到已知托管提供程序本机类型的映射。我是错误部分的基础

    private void button1_Click(object sender, EventArgs e)
    {
        String connectionString = @"Connection String Here ";
        SqlConnection connection = new SqlConnection(connectionString);
        connection.Open();

        // INSERTION 
        string query = "INSERT INTO StudentMaster(RollNo,Name,Gender,FathersName,Course,Branch,Semester,Section,ContactNo1,ContactNo2,EmailId) VALUES ('" + textBox1.Text + "', '" + textBox2.Text + "', @Gender,'" + textBox3.Text + "', '" + comboBox1.Text + "','" + comboBox2.Text + "', '" + comboBox3.Text + "', '" + comboBox4.Text + "','" + textBox4.Text + "', '" + textBox5.Text + "', '" + textBox6.Text + "'";
        SqlCommand command = new SqlCommand(query, connection);

        // Radio button
        if (radioButton1.Checked)
        {
            command.Parameters.AddWithValue("@Gender", "Male");
        }
        else
        {
            command.Parameters.AddWithValue("@Gender", "Female");
        }

        // value store for combobox
        //command.Parameters.AddWithValue("@DOB", dateTimePicker1.Text);
        command.Parameters.AddWithValue("@Course", comboBox1.SelectedItem);
        command.Parameters.AddWithValue("@Branch", comboBox2.SelectedItem);
        command.Parameters.AddWithValue("@Semester", comboBox3.SelectedItem);
        command.Parameters.AddWithValue("@Section", comboBox4.SelectedItem);

        command.ExecuteNonQuery();
        connection.Close();

        if (MessageBox.Show("Do you really want to INSERT??", "Insert", MessageBoxButtons.OKCancel) == DialogResult.OK)
        {
            MessageBox.Show("INSERTED");
        }
    }

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我自己解决了这个问题：

command.Parameters.AddWithValue("@Course", comboBox1.Text);
command.Parameters.AddWithValue("@Branch", comboBox2.Text);
command.Parameters.AddWithValue("@Semester", comboBox3.Text);
command.Parameters.AddWithValue("@Section", comboBox4.Text);

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SelectedValue是用作DataRow的DataRowView视图的类的对象，应以相同的方式使用，即：  

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DataRowView drv=（DataRowView）comboBox1.SelectedValue

sql命令字符串中的参数

@branch、@sement、@section

在哪里？string query=“插入StudentMaster（RollNo、Name、Gender、fathername、Course、branch、sement、section、ContactNo1、ContactNo2、EmailId）值（“+textBox1.Text+”、“+textBox2.Text+”、@Gender、“+textBox3.Text+”、“+comboBox1.Text+”、“，”“+comboBox2.Text+”、“+comboBox3.Text+”、“+comboBox4.Text+”、“+textBox4.Text+”、“+textBox5.Text+”、“+textBox6.Text+”；@rs:wht发生了什么？”？？？？？？？？