Question

我正在处理一个个人项目，该项目使用Microsoft SQL DB和Web层进行Rest API调用。我正在尝试使用SqlDataReader从数据库获取int32s和字符串。当我读字符串时，没有错误，但是当我尝试读整数时，我得到以下

`异常：System.IndexOutOfRangeException：'StudentID'

public StudentAccount FindStudentByID(int id)
{
    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        connection.Open();
        String sql = "SELECT FirstName, LastName,StudentBiography FROM [PersonTest].[dbo].[StudentAccounts] WHERE StudentID = @p1";
        StudentAccount matchingStudent = new StudentAccount();

        using (SqlCommand cmd = new SqlCommand(sql, connection))
        {
            cmd.Parameters.Add("@p1", SqlDbType.Int).Value = id;
            cmd.CommandType = CommandType.Text;

            SqlDataReader reader = cmd.ExecuteReader();

                while (reader.Read())
                {
                    matchingStudent.StudentID = reader.GetInt32(reader.GetOrdinal("StudentID"));

                    matchingStudent.FirstName = reader["FirstName"].ToString();
                    matchingStudent.LastName = reader["LastName"].ToString();
                    matchingStudent.Biography = reader["StudentBiography"].ToString();

                    matchingStudent.CollegeID = reader.GetInt32(reader.GetOrdinal("COLLTB_CollegeID"));
                }

            reader.Close();

            return matchingStudent;
        }
    }
}

StudentAccounts表如下：

StudentAccounts (StudentID, FirstName, LastName, StudentBiography, CollTB_CollegeID)

StudentID是主键。

如果我弄乱了格式或任何内容，我会提前道歉，这是我第一次在该论坛上发帖。谢谢！

Answer 1

您没有将StudentID语句中的列返回COLLTB_CollegeID或select ...

String sql = "SELECT FirstName, LastName,StudentBiography FROM [PersonTest].[dbo].[StudentAccounts] WHERE StudentID = @p1";

应该是...

String sql = "SELECT StudentID, FirstName, LastName, StudentBiography, COLLTB_CollegeID FROM [PersonTest].[dbo].[StudentAccounts] WHERE StudentID = @p1";

尽管您似乎两次设置了matchingStudent.CollegeID，但看起来您返回列中的StudentID看起来仍然没有！

Answer 2

您正在使用：

matchingStudent.CollegeID = reader.GetInt32(reader.GetOrdinal("StudentID"));

这意味着：

var columnNumber = reader.GetOrdinal("StudentID");
matchingStudent.CollegeID = reader.GetInt32(columnNumber);

现在，第一次呼叫失败，因为StudentID语句中没有SELECT。包括要阅读的列。 COLLTB_CollegeID也是如此。

所以：

var sql = "SELECT FirstName, LastName, StudentBiography, StudentID, COLLTB_CollegeID FROM [PersonTest].[dbo].[StudentAccounts] WHERE StudentID = @p1";

此外，您正在将结果分配给错误的属性：

matchingStudent.StudentID = reader.GetInt32(reader.GetOrdinal("StudentID"));

如何从SqlDataReader获取int32和字符串。收到错误System.IndexOutOfRangeException：'StudentID'

2 个答案: