如何找到違反約束的列？

Question

我有一個強類型數據集，其引發此錯誤空值，

System.Data.ConstraintException：未能啓用約束。一個或多個行包含違反非空，唯一或外鍵約束的值。在System.Data.DataTable.EnableConstraints（）處 System.Data.Common.DataAdapter.FillFromReader System.Data.DataTable.EndLoadData（）（數據集的數據集，數據表 數據表，字符串srcTable要，DataReaderContainer的DataReader， 的Int32 startRecord， INT32最大記錄，的DataColumn parentChapterColumn， 對象parentChapterValue）在 System.Data.Common.DataAdapter.Fill（數據表[]數據表， IDataReader的DataReader的，INT32 startRecord，INT32最大記錄）在 System.Data.Common.DbDataAdapter.FillInternal（數據集數據集， DataTable [] datatables，Int32 startRecord，Int32 maxRecords，字符串 srcTable，IDbCommand命令，CommandBehavior行爲）在 System.Data.Com mon.DbDataAdapter.Fill（數據表[]數據表，的Int32 startRecord，的Int32最大記錄，IDbCommand的命令，的CommandBehavior 行爲）在System.Data.Common.DbDataAdapter.Fill（數據表 的dataTable）在 Fruits.DataAccess.FruitsTableAdapters.FruitsExtTableAdapter。 GetFruits（字符串 用戶，字符串濾波器）在 Fruits.DataAccess.FruitsDataAccess.GetFruits（字符串用戶，字符串 濾波器）在Fruits.WebServices.External.Fruity.GetFruits（字符串 濾波器）

所有的列用1單行填充我正在測試它，

USE [FruitDataBase] 
GO 

SET ANSI_NULLS ON 
GO 

SET QUOTED_IDENTIFIER ON 
GO 

CREATE TABLE [dbo].[Fruits](
    [ID] [int] NOT NULL, 
    [CategoryID] [int] NOT NULL, 
    [Title] [nvarchar](255) NOT NULL, 
    [URL] [nvarchar](255) NOT NULL, 
    [Status] [nvarchar](70) NOT NULL, 
    [Description] [nvarchar](1024) NULL, 
    [User1] [nvarchar](50) NOT NULL, 
    [Date] [datetime] NOT NULL, 
    [User2] [nvarchar](50) NULL, 
    [Date2] [datetime] NULL, 
    [Impact] [nvarchar](255) NULL, 
    [Solution] [nvarchar](1024) NULL, 
CONSTRAINT [PK_Fruits] PRIMARY KEY CLUSTERED 
(
    [ID] ASC 
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] 
) ON [PRIMARY] 

GO 

ALTER TABLE [dbo].[Fruits] WITH CHECK ADD CONSTRAINT [FK_Fruits_Categories] FOREIGN KEY([CategoryID]) 
REFERENCES [dbo].[Categories] ([ID]) 
GO 

ALTER TABLE [dbo].[Fruits] CHECK CONSTRAINT [FK_Fruits_Categories] 
GO 

Answer 1

你可以在你的代碼中使用此方法。 .NET檢查數據集以拋出異常。

 public void CheckDataSet(DataSet dataSet) 
     {                
     Assembly assembly = Assembly.LoadFrom(@"C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.0\System.Data.dll"); 
     Type type = assembly.GetType("System.Data.ConstraintEnumerator"); 
     ConstructorInfo ctor = type.GetConstructor(new[] { typeof(DataSet) }); 
     object instance = ctor.Invoke(new object[] { dataSet });     
     BindingFlags bf = BindingFlags.Instance | BindingFlags.Public; 
     MethodInfo m_GetNext = type.GetMethod("GetNext", bf); 

     while ((bool)m_GetNext.Invoke(instance, null)) 
     { 
      bool flag = false; 
      MethodInfo m_GetConstraint = type.GetMethod("GetConstraint", bf);      
      Constraint constraint = (Constraint) m_GetConstraint.Invoke(instance, null); 
      Type constraintType = constraint.GetType(); 
      BindingFlags bfInternal = BindingFlags.Instance | BindingFlags.NonPublic; 
      MethodInfo m_IsConstraintViolated = constraintType.GetMethod("IsConstraintViolated", bfInternal);      
      flag = (bool)m_IsConstraintViolated.Invoke(constraint, null); 
      if (flag)      
       Debug.WriteLine("Constraint violated, ConstraintName: " + constraint.ConstraintName + ", tableName: " + constraint.Table);            
     } 

     foreach (DataTable table in dataSet.Tables) 
     { 
      foreach (DataColumn column in table.Columns) 
      { 
       Type columnType = column.GetType(); 
       BindingFlags bfInternal = BindingFlags.Instance | BindingFlags.NonPublic; 

       bool flag = false; 
       if (!column.AllowDBNull) 
       {        
        MethodInfo m_IsNotAllowDBNullViolated = columnType.GetMethod("IsNotAllowDBNullViolated", bfInternal);               
        flag = (bool)m_IsNotAllowDBNullViolated.Invoke(column, null); 
        if (flag) 
        { 
         Debug.WriteLine("DBnull violated --> ColumnName: " + column.ColumnName + ", tableName: " + column.Table.TableName); 
        } 
       } 
       if (column.MaxLength >= 0) 
       { 
        MethodInfo m_IsMaxLengthViolated = columnType.GetMethod("IsMaxLengthViolated", bfInternal);        
        flag = (bool)m_IsMaxLengthViolated.Invoke(column, null);        
        if (flag)        
         Debug.WriteLine("MaxLength violated --> ColumnName: " + column.ColumnName + ", tableName: " + column.Table.TableName); 
       } 
      } 
     }              
} 

Answer 2

問題在於其中一個列名稱在數據集中不匹配，不知道是什麼觸發了它，但匹配列的名稱和返回的列名解決了問題。

我還使用強類型數據集的「預覽數據」功能，幫助我找出問題所在。

Answer 3

DataSet/DataTable有屬性可以獲取有關錯誤的更多詳細信息。

因此，這些細節本身並不屬於例外本身，因爲你可以這麼想，這就是訣竅。見http://www.codeproject.com/Tips/405938/Debugging-DataSet-Constraint-Errors

樣品：

catch (ConstraintException) 
{ 
    DataRow[] rowErrors = this.YourDataSet.YourDataTable.GetErrors(); 

    System.Diagnostics.Debug.WriteLine("YourDataTable Errors:" 
     + rowErrors.Length); 

    for (int i = 0; i < rowErrors.Length; i++) 
    { 
     System.Diagnostics.Debug.WriteLine(rowErrors[i].RowError); 

     foreach (DataColumn col in rowErrors[i].GetColumnsInError()) 
     { 
      System.Diagnostics.Debug.WriteLine(col.ColumnName 
       + ":" + rowErrors[i].GetColumnError(col)); 
     } 
    } 
}