Question

ABC的值（参数）可以为NULL。我正在努力将其设置为null。以下声明无效。如果我尝试设置类型Nullable（OfInteger），我得到的错误是该值是'错误的类型'。提前谢谢。

 Dim ABC as Integer = Nothing

 Public Function RunStoredProce(ByVal **ABC** As Integer, ByVal DEF As String) _
               As IEnumerable(Of MyProjectStoredProcResults) Implements MyFunction.GetThatDataResult

        Dim y = (From p In dc.uspReportMyFunction(**ABC**, DEF)
            Select p).ToList

        Return y

    End Function

Answer 1

Dim ABC As Nullable(Of Integer)

Public Function RunStoredProce(ByVal ABC As Nullable(Of Integer), ByVal DEF As String) _
           As IEnumerable(Of MyProjectStoredProcResults) Implements MyFunction.GetThatDataResult

    Dim y = (From p In dc.uspReportMyFunction(ABC, DEF)
        Select p).ToList

    Return y

End Function

我相信linqtosql会自动处理可空的翻译。

Answer 2

你可以使整数可以为空，只有在它有值时才传递它：

请注意ABC如何以Nullable类型传递：

Public Function RunStoredProce(ByVal ABC As Integer?, ByVal DEF As String) As IEnumerable(Of MyProjectStoredProcResults) Implements MyFunction.GetThatDataResult
    Return (From p In dc.uspReportMyFunction(ABC, DEF) Select p).ToList
End Function

我不知道你是如何设置系统的，但假设uspReportMyFunction是调用存储过程的函数，你可能希望在它为空时排除ABC：

If ABC.HasValue Then
    'Add ABC as a parameter
End If

'Add DEF as a parameter

'Execute the stored procedure

修改

假设这是执行存储过程的数据函数

public void SaveSomething(int jobID, int? postNumber) { using (var data = new DataAccess(this.ConnectionString)) { data.ProcedureName = "SaveSomething"; data.AddParm("@JobID", SqlDbType.Int, JobID); if (postNumber.HasValue) data.AddParm("@PostNumber", SqlDbType.Int, PostNumber.GetValueOrDefault()); return data.ExecNonQuery(); } }

从前端，你可以这样调用这个函数：

int jobID = 1; int? postNumber = null; GetWorkOrderDetailAdjustment(jobID, postNumber); //postNumber == null

ASP.Net VB存储过程允许空参数 - 如何将NULL整数传递给存储过程

2 个答案: