[英]C# IDataReader System.IndexOutOfRangeException Problem
我在 C# 中使用 IDataReader 时遇到了 IndexOutOfRangeException 问题。下面是我的示例代码。 代码在执行GetDataValue的功能时向我抛出异常。
public List<Users> SelectUsersbyUsernamePassword(string username, string password)
{
const string SQL_STATEMENT =
"SELECT U.Username, U.Password, U.Role " +
"FROM Users U ";
List<Users> listusers = new List<Users>();
Database db = new Microsoft.Practices.EnterpriseLibrary.Data.Sql.SqlDatabase(CONNECTION_NAME);
using (DbCommand cmd = db.GetSqlStringCommand(SQL_STATEMENT))
{
db.AddInParameter(cmd, "@username", DbType.String, username);
db.AddInParameter(cmd, "@password", DbType.String, password);
try
{
using (IDataReader dr = db.ExecuteReader(cmd))
{
while (dr.Read())
{
Users users = new Users();
users.UserID = base.GetDataValue<int>(dr, "UserID");
users.Username = base.GetDataValue<string>(dr, "Username");
users.Password = base.GetDataValue<string>(dr, "Password");
users.Role = base.GetDataValue<string>(dr, "Role");
listusers.Add(users);
}
}
}
catch (Exception ex)
{
throw ex;
//throw new DbException(ex.Message, SQL_STATEMENT, "username = " + username, ex.InnerException);
}
}
return listusers;
}
数据访问
protected T GetDataValue<T>(IDataReader dr, string columnName)
{
int i = dr.GetOrdinal(columnName);
if (!dr.IsDBNull(i))
return (T)dr.GetValue(i);
else
return default(T);
}
根据@Dai 的评论,IndexOutOfRangeException 问题已解决,这是由于 SELECT 查询未获得正确的列。
// Read values.
users.UserID = base.GetDataValue<int>(dr, "UserID");
users.Username = base.GetDataValue<string>(dr, "Username");
users.Password = base.GetDataValue<string>(dr, "Password");
users.Role = base.GetDataValue<string>(dr, "Role");
SQL 查询(待定)
const string SQL_STATEMENT =
"SELECT U.UserID, U.Username, U.Password, U.Role " +
"FROM Users U " +
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