返回正确列数时的 SqlDataReader 索引超出范围异常

Question

我有一个返回正确列数的存储过程，但下面的代码大部分时间都有效，但 RANDOMLY 在下面抛出异常。我们最近升级到 .NET 4.6，之后我们注意到异常。

问题：

1 异常发生的位置和原因？

2 根据底部的源码，SQL客户端怎么可能从服务器端接收到空的metaData？

存储过程GetUser:

CREATE PROCEDURE [dbo].[GetUser]    
    @UserID int
AS
BEGIN

    SET NOCOUNT ON;

    DECLARE @UserIDChar NVARCHAR(255);
    SET @UserIDChar = convert(nvarchar(255), @UserID);

    SELECT TOP 1
        A.Value1 As FirstName, 
        A.Value2 As LastName
       -- three more columns omitted here
    FROM dbo.Activity as A      
    WHERE A.ActivityValue = @UserIDChar  --ActivityValue is NVARCHAR(255) type
    ORDER BY A.DateCreated DESC 

    SET NOCOUNT OFF;

END 

C#网络层：

using (var cn = new SqlConnection(ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString))
{
    SqlCommand cmd = new SqlCommand();
    cmd.CommandType = CommandType.StoredProcedure;
    cmd.CommandText = "GetUser";  //the proc returns one row that consists of two columns
    cmd.Connection = cn;
    cmd.Parameters.AddWithValue("@UserID", userId);

    cn.Open();

    using (IDataReader dr = cmd.ExecuteReader(CommandBehavior.SingleResult))
    {
        if (dr.Read())  //check if row is available
        {
            string firstName = (string)dr[0];
            string lastName = (string)dr[1];                        
            // three more columns omitted here
            return firstName + " " + lastName;
        }
    }
}

错误：

异常类型：System.IndexOutOfRangeException
消息：索引超出了数组的范围。
数据：System.Collections.ListDictionaryInternal
TargetSite: Void CheckDataIsReady(Int32, Boolean, Boolean, System.String)
来源：System.Data

源码如下：

private void CheckDataIsReady(int columnIndex, bool allowPartiallyReadColumn = false, bool permitAsync = false, string methodName = null) {
            if (_isClosed) {
                throw ADP.DataReaderClosed(methodName ?? "CheckDataIsReady");
            }
            if ((!permitAsync) && (_currentTask != null)) {
                throw ADP.AsyncOperationPending();
            }
            Debug.Assert(!_sharedState._dataReady || _metaData != null, "Data is ready, but there is no metadata?");
            if ((!_sharedState._dataReady) || (_metaData == null)) {
                throw SQL.InvalidRead();
            }
            if ((columnIndex < 0) || (columnIndex >= _metaData.Length)) {
                throw ADP.IndexOutOfRange();
            }
            if ((IsCommandBehavior(CommandBehavior.SequentialAccess)) &&                                    // Only for sequential access
                ((_sharedState._nextColumnDataToRead > columnIndex) || (_lastColumnWithDataChunkRead > columnIndex) ||   // Read past column
                ((!allowPartiallyReadColumn) && (_lastColumnWithDataChunkRead == columnIndex)) ||           // Partially read column
                ((allowPartiallyReadColumn) && (HasActiveStreamOrTextReaderOnColumn(columnIndex))))) {      // Has a Stream or TextReader on a partially-read column
                    throw ADP.NonSequentialColumnAccess(columnIndex, Math.Max(_sharedState._nextColumnDataToRead, _lastColumnWithDataChunkRead + 1));
            }
        }

http://referencesource.microsoft.com/#System.Data/System/Data/SqlClient/SqlDataReader.cs,577d642dce99ed0d

Answer 1

缺少架构名称可能会惹恼你。

另外，下面的 C# 代码中的一些调试技巧。

1. 为存储过程提供架构名称。

   IF EXISTS (
               SELECT * FROM INFORMATION_SCHEMA.ROUTINES
               WHERE ROUTINE_TYPE = N'PROCEDURE' and ROUTINE_SCHEMA = N'dbo' and ROUTINE_NAME = N'GetUser'  
           )   
   BEGIN
       DROP PROCEDURE [dbo].[GetUser]
   END
   
   GO
   
   CREATE PROCEDURE dbo.GetUser()
   
   AS 
   
   SELECT TOP 1
       FirstName, LastName
   FROM 
       User
   --omitted WHERE userid = @id
   
   
   GO
   

2. 将你的 c# 更改为：

      using (var cn = new SqlConnection(ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString))
     {
          SqlCommand cmd = new SqlCommand();
          cmd.CommandType = CommandType.StoredProcedure;
          cmd.CommandText = "dbo.GetUser";  
          cmd.Connection = cn;
   
          cn.Open();
   
          using (IDataReader dr = cmd.ExecuteReader())
          {
          while (dr.Read()) 
                              string temp = string.Empty;
   
       int fc = dr.FieldCount;    
       if (fc>0)
       {
                       object val2 = dr[0];
                       temp = val1.GetType().ToString();
       }
   
       if (fc>1)
       {
                       object val2 = dr[1];
                       temp = val2.GetType().ToString();
       }
   
   
   
       temp = "did I get here?";
   
       string firstName = (string)dr[0];
       string lastName = (string)dr[1];                        
   
       return firstName + " " + lastName;
   }
          }
          }
   

Answer 2

我认为这一行在你的存储过程中搞砸了：

A.Value2 广告姓氏

应该是： A.Value2 作为 LastName

Answer 3

你没有在C#代码中指定参数userid请使用CommandParameter然后尝试做

Answer 4

试试看
可能无法修复，但你会得到信息，至少它会优雅地失败

try
{ 
    cn.Open();
    string firstName = "not";
    string lastName = "found";
    using (SQLDataReader dr = cmd.ExecuteReader(CommandBehavior.SingleResult))
    {
        if (dr.Read())  //if there is a row, there are two columns. Thus index is used below
        {
            Debug.WriteLine(dr.FieldCount);
            firstName = rdr.IsDBNull(0) ? string.Empty : rdr.GetString(0);
            lastName = rdr.IsDBNull(1) ? string.Empty : rdr.GetString(1);                         
        }
    }
} 
catch (SqlException ex)
{
    Debug.WriteLine("GetUser " + Environment.NewLine + ex.Message);
}
catch (Exception ex)
{
    Debug.WriteLine("GetUser" + Environment.NewLine + ex.Message);
    throw ex;
}
finally
{
    cn.Close();
}
return firstName + " " + lastName;