Question

我正在尝试从多个表中计算记录并将结果返回到输出参数，以便我可以在Visual Studio C＃中使用它们。

下面是T-SQL和C＃代码：

T-SQL代码：

ALTER PROCEDURE CountRecordsForUpdates
    @AreaOfLaw AS numeric OUTPUT,
    @SubjectMatter AS numeric OUTPUT,
    @Principles AS numeric OUTPUT,
    @Judges AS numeric OUTPUT,
    @Courts AS numeric OUTPUT
AS
    DECLARE @AreaOfLawOut AS numeric
    DECLARE @SubjectMatterOut AS numeric
    DECLARE @PrinciplesOut AS numeric
    DECLARE @JudgesOut AS numeric
    DECLARE @CourtsOut AS numeric
    DECLARE @CasesOut AS numeric
    DECLARE @ReportsOut AS numeric
    DECLARE @IssuesDiscussedOut AS numeric
    --DECLARE @Judgement AS numeric
BEGIN
    SET NOCOUNT ON;

    SELECT @AreaOfLawOut = COUNT(AoLId) FROM [dbo].[CLR.AreaOfLaw] OUTPUT
    SELECT @SubjectMatterOut = COUNT(SMId) FROM [dbo].[CLR.SubjectMatter] OUTPUT
    SELECT @PrinciplesOut = COUNT(PId) FROM [dbo].[CLR.Principle] OUTPUT
    SELECT @JudgesOut = COUNT(JId) FROM LocalJudgesView OUTPUT
    SELECT @CourtsOut = COUNT(CourtId) FROM LocalCourtView OUTPUT
    SELECT @CasesOut = COUNT(CaseId) FROM LocalReportedCaseView OUTPUT
    SELECT @ReportsOut = COUNT(ReportId) FROM LocalReportView OUTPUT
    SELECT @IssuesDiscussedOut = COUNT(IDId) FROM CLR_IssuesDiscussedView OUTPUT
END
GO

C＃代码：

try
{
    decimal aol = 0, sm = 0, p = 0, judge = 0, court = 0;

    using (SqlConnection sqlConnection = new SqlConnection(DataSources.RemoteConnectionString()))
    {
        sqlConnection.Open();

        using (SqlCommand sqlCommand = new SqlCommand("[DB7934_businessmind].[CountRecordsForUpdates]", sqlConnection))
        {
            sqlCommand.CommandType = System.Data.CommandType.StoredProcedure;

            SqlParameter aolParam = new SqlParameter("@AreaOfLaw", aol) { Direction = System.Data.ParameterDirection.Output };
            sqlCommand.Parameters.Add(aolParam);

            SqlParameter smParam = new SqlParameter("@SubjectMatter", sm) { Direction = System.Data.ParameterDirection.Output };
            sqlCommand.Parameters.Add(smParam);

            SqlParameter pParam = new SqlParameter("@Principles", p) { Direction = System.Data.ParameterDirection.Output };
            sqlCommand.Parameters.Add(pParam);

            SqlParameter judgeParam = new SqlParameter("@Judges", judge) { Direction = System.Data.ParameterDirection.Output };
            sqlCommand.Parameters.Add(judgeParam);

            SqlParameter courtParam = new SqlParameter("@Courts", court) { Direction = System.Data.ParameterDirection.Output };
            sqlCommand.Parameters.Add(courtParam);

            sqlCommand.ExecuteNonQuery();
            sqlCommand.Dispose();

            AoLRemoteCount = Convert.ToDecimal(aolParam.Value);
            SMRemoteCount = Convert.ToDecimal(smParam.Value);
            PRemoteCount = Convert.ToDecimal(pParam.Value);
            CourtRemoteCount = Convert.ToDecimal(courtParam.Value);
            JRemoteCount = Convert.ToDecimal(judgeParam.Value);
        }

        sqlConnection.Close();
    }
}
catch(Exception ex)
{
    MessageBox.Show("An error has occurred while counting cloud records, the original error is: "
        + ex.Message, "Cloud Records", MessageBoxButtons.OK, MessageBoxIcon.Error);
}

当我运行代码时，收到以下错误消息：

无法将对象从DBNull强制转换为其他类型。

我已经尝试了所有我能想到但无济于事的东西。我需要帮助。我能够一个接一个地计算它们，但这意味着我每次都要拨打互联网上的数据库，我认为这对流量没有好处。

我想要的只是一次性我能够计算大约6个表中的所有记录并返回值，以便我可以将它们分配给c＃中的属性以供将来使用。

Answer 1

当数据库中的值为NULL时，它将以DBNull的形式返回。你必须相应地检查：

SMRemoteCount = !DBNull.Value.Equals(smParam.Value) ? Convert.ToDecimal(smParam.Value) : 0m;

<强>更新

您还必须确保在存储过程中分配返回值：

ALTER PROCEDURE CountRecordsForUpdates
-- Add the parameters for the stored procedure here
@AreaOfLaw AS numeric OUTPUT,
@SubjectMatter AS numeric OUTPUT,
@Principles AS numeric OUTPUT,
@Judges AS numeric OUTPUT,
@Courts AS numeric OUTPUT

AS
DECLARE @CasesOut AS numeric
DECLARE @ReportsOut AS numeric
DECLARE @IssuesDiscussedOut AS numeric
--DECLARE @Judgement AS numeric
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;

-- Insert statements for procedure here
SELECT @AreaOfLaw = COUNT(AoLId) FROM [dbo].[CLR.AreaOfLaw] OUTPUT
SELECT @SubjectMatter = COUNT(SMId) FROM [dbo].[CLR.SubjectMatter] OUTPUT
SELECT @Principles = COUNT(PId) FROM [dbo].[CLR.Principle] OUTPUT
SELECT @Judges = COUNT(JId) FROM LocalJudgesView OUTPUT
SELECT @Courts = COUNT(CourtId) FROM LocalCourtView OUTPUT
SELECT @CasesOut = COUNT(CaseId) FROM LocalReportedCaseView OUTPUT
SELECT @ReportsOut = COUNT(ReportId) FROM LocalReportView OUTPUT
SELECT @IssuesDiscussedOut = COUNT(IDId) FROM CLR_IssuesDiscussedView OUTPUT
END
GO

计算SQL Server记录并按输出参数返回结果

1 个答案: