问题描述

我正在尝试从我的 C# Windows 应用程序中调用存储过程.存储过程在 SQL Server 2008 的本地实例上运行.我能够调用存储过程，但无法从存储过程中检索返回值.这个存储过程应该返回序列中的下一个数字.我在网上做了研究，我看到的所有网站都指出这个解决方案是有效的.

I am trying to call a stored procedure from my C# windows application. The stored procedure is running on a local instance of SQL Server 2008. I am able to call the stored procedure but I am not able to retrieve the value back from the stored procedure. This stored procedure is supposed to return the next number in the sequence. I have done research online and all the sites I've seen have pointed to this solution working.

存储过程代码:

ALTER procedure [dbo].[usp_GetNewSeqVal]
      @SeqName nvarchar(255)
as
begin
      declare @NewSeqVal int
      set NOCOUNT ON
      update AllSequences
      set @NewSeqVal = CurrVal = CurrVal+Incr
      where SeqName = @SeqName

      if @@rowcount = 0 begin
print 'Sequence does not exist'
            return
      end

      return @NewSeqVal
end

调用存储过程的代码:

SqlConnection conn = new SqlConnection(getConnectionString());
conn.Open();

SqlCommand cmd = new SqlCommand(parameterStatement.getQuery(), conn);
cmd.CommandType = CommandType.StoredProcedure;

SqlParameter param = new SqlParameter();

param = cmd.Parameters.Add("@SeqName", SqlDbType.NVarChar);
param.Direction = ParameterDirection.Input;
param.Value = "SeqName";

SqlDataReader reader = cmd.ExecuteReader();

我也尝试过使用 DataSet 来检索具有相同结果的返回值.我想得到什么我的存储过程的返回值?如果需要更多信息，请告诉我.

I have also tried using a DataSet to retrieve the return value with the same result. What am I missing to get the return value from my stored procedure? If more information is needed, please let me know.

推荐答案

需要在命令中添加返回参数:

You need to add return parameter to the command:

using (SqlConnection conn = new SqlConnection(getConnectionString()))
using (SqlCommand cmd = conn.CreateCommand())
{
    cmd.CommandText = parameterStatement.getQuery();
    cmd.CommandType = CommandType.StoredProcedure;
    cmd.Parameters.AddWithValue("SeqName", "SeqNameValue");

    var returnParameter = cmd.Parameters.Add("@ReturnVal", SqlDbType.Int);
    returnParameter.Direction = ParameterDirection.ReturnValue;

    conn.Open();
    cmd.ExecuteNonQuery();
    var result = returnParameter.Value;
}

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