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IQueryableオブジェクトをに変換しようとしていますDataTable。に変換したいクエリの例を次に示しますDataTable。

var query = DbContext.SomeObjectSet.Select(x => new { PropertyName1 = x.ColumnName1, PropertyName2 = x.ColumnName2 });

Selectメソッドで作成される匿名オブジェクトとプロパティの名前に注意してください。

new { PropertyName1 = x.ColumnName1, PropertyName2 = x.ColumnName2 }

IQueryableこの問題をグーグルで調べた後、オブジェクトを に変換する次のコードに出くわしましたDataTable。

public static DataTable EntityToDatatable(this IQueryable result)
{
    ObjectQuery query = (result as ObjectQuery);

    ObjectContext context = query.Context;

    EntityConnection entityCon = (context.Connection as EntityConnection);

    using (SqlConnection sqlCon = new SqlConnection(entityCon.StoreConnection.ConnectionString))
    {
        using (SqlCommand cmd = new SqlCommand(query.ToTraceString(), sqlCon))
        {
            foreach (var param in query.Parameters)
            {
                cmd.Parameters.AddWithValue(param.Name, param.Value);

            }

            using (SqlDataAdapter dataAdapter = new SqlDataAdapter(cmd))
            {
                using (DataTable dataTable = new DataTable())
                {
                    dataAdapter.Fill(dataTable);

                    return dataTable;

                }

            }

        }

    }

}

上記のコードは「動作」し、ToTraceString()メソッドからの SQL ステートメントは次のとおりです。

SELECT [Extent1].[ColumnName1] AS [ColumnName1], [Extent1].[ColumnName2] AS [ColumnName2] FROM [dbo].[TableName] AS [Extent1]

問題: SQL ステートメントの列名 (つまりcolumnName1および) が、 でまたはメソッドが呼び出された場合に実体化されるオブジェクト (つまりおよび)columnName2のプロパティの名前に対応していません。SQL ステートメントの列が匿名オブジェクトのプロパティと同じ順序である場合、これはそれほど悪くはありませんが、常にそうとは限りません。どこか (IQueryable オブジェクトの内部だと思います) に、SQL ステートメントの列名と結果の匿名オブジェクト プロパティ名の間にマッピングが必要です。PropertyName1PropertyName2ToList()AsEnumerable()query

このマッピングを取得する方法を知っている人はいますか?

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1 に答える 1

2

私は自分の問題の解決策を見つけることができました：

まず、匿名オブジェクト プロパティの位置を SQL ステートメントの列位置にマップする次のコードが必要です ( Entity Framework はクエリ結果のマッピングを匿名型にどのように管理しますか? から)。

public static Int32[] GetPropertyPositions(this ObjectQuery query)
{
    // get private ObjectQueryState ObjectQuery._state; 
    // of actual type internal class 
    //      System.Data.Objects.ELinq.ELinqQueryState 

    Object queryState = GetProperty(query, "QueryState");
    AssertNonNullAndOfType(queryState, "System.Data.Objects.ELinq.ELinqQueryState");

    // get protected ObjectQueryExecutionPlan ObjectQueryState._cachedPlan; 
    // of actual type internal sealed class 
    //      System.Data.Objects.Internal.ObjectQueryExecutionPlan 
    Object plan = GetField(queryState, "_cachedPlan");
    AssertNonNullAndOfType(plan, "System.Data.Objects.Internal.ObjectQueryExecutionPlan");

    // get internal readonly DbCommandDefinition ObjectQueryExecutionPlan.CommandDefinition; 
    // of actual type internal sealed class 
    //      System.Data.EntityClient.EntityCommandDefinition 
    Object commandDefinition = GetField(plan, "CommandDefinition");
    AssertNonNullAndOfType(commandDefinition, "System.Data.EntityClient.EntityCommandDefinition");

    // get private readonly IColumnMapGenerator EntityCommandDefinition._columnMapGenerator; 
    // of actual type private sealed class 
    //      System.Data.EntityClient.EntityCommandDefinition.ConstantColumnMapGenerator 
    Object columnMapGenerator = GetField(commandDefinition, "_columnMapGenerator");
    AssertNonNullAndOfType(columnMapGenerator, "System.Data.EntityClient.EntityCommandDefinition+ConstantColumnMapGenerator");

    // get private readonly ColumnMap ConstantColumnMapGenerator._columnMap; 
    // of actual type internal class 
    //      System.Data.Query.InternalTrees.SimpleCollectionColumnMap 
    Object columnMap = GetField(columnMapGenerator, "_columnMap");
    AssertNonNullAndOfType(columnMap, "System.Data.Query.InternalTrees.SimpleCollectionColumnMap");

    // get internal ColumnMap CollectionColumnMap.Element; 
    // of actual type internal class 
    //      System.Data.Query.InternalTrees.RecordColumnMap 
    Object columnMapElement = GetProperty(columnMap, "Element");
    AssertNonNullAndOfType(columnMapElement, "System.Data.Query.InternalTrees.RecordColumnMap");

    // get internal ColumnMap[] StructuredColumnMap.Properties; 
    // array of internal abstract class 
    //      System.Data.Query.InternalTrees.ColumnMap 
    Array columnMapProperties = GetProperty(columnMapElement, "Properties") as Array;
    AssertNonNullAndOfType(columnMapProperties, "System.Data.Query.InternalTrees.ColumnMap[]");

    Int32 n = columnMapProperties.Length;

    Int32[] propertyPositions = new Int32[n];

    for (Int32 i = 0; i < n; ++i)
    {
        // get value at index i in array 
        // of actual type internal class 
        //      System.Data.Query.InternalTrees.ScalarColumnMap 
        Object column = columnMapProperties.GetValue(i);
        AssertNonNullAndOfType(column, "System.Data.Query.InternalTrees.ScalarColumnMap");

        //string colName = (string)GetProp(column, "Name"); 
        // can be used for more advanced bingings 

        // get internal int ScalarColumnMap.ColumnPos; 
        Object columnPositionOfAProperty = GetProperty(column, "ColumnPos");
        AssertNonNullAndOfType(columnPositionOfAProperty, "System.Int32");

        propertyPositions[i] = (int)columnPositionOfAProperty;

    }

    return propertyPositions;

}

static object GetProperty(object obj, string propName)
{
    PropertyInfo prop = obj.GetType().GetProperty(propName, BindingFlags.NonPublic | BindingFlags.Instance);
    if (prop == null) throw EFChangedException();
    return prop.GetValue(obj, new object[0]);

}

static object GetField(object obj, string fieldName)
{
    FieldInfo field = obj.GetType().GetField(fieldName, BindingFlags.NonPublic | BindingFlags.Instance);
    if (field == null) throw EFChangedException();
    return field.GetValue(obj);

}

static void AssertNonNullAndOfType(object obj, string fullName)
{
    if (obj == null) throw EFChangedException();
    string typeFullName = obj.GetType().FullName;
    if (typeFullName != fullName) throw EFChangedException();

}

static InvalidOperationException EFChangedException()
{
    return new InvalidOperationException("Entity Framework internals has changed, please review and fix reflection code");

}

次にEntityToDatatable、次のようにメソッドを変更できます。

public static DataTable EntityToDatatable(this IQueryable query)
{
    SqlConnection sqlConnection = null;
    SqlCommand sqlCommand = null;
    SqlDataAdapter sqlDataAdapter = null;
    DataTable dataTable = null;

    try
    {
        ObjectQuery objectQuery = (query as ObjectQuery);

        ObjectContext objectContext = objectQuery.Context;

        EntityConnection entityConnection = (objectContext.Connection as EntityConnection);

        sqlConnection = new SqlConnection(entityConnection.StoreConnection.ConnectionString);

        sqlCommand = new SqlCommand(objectQuery.ToTraceString(), sqlConnection);

        foreach (var parameter in objectQuery.Parameters)
        {
            sqlCommand.Parameters.AddWithValue(parameter.Name, parameter.Value);

        }

        sqlDataAdapter = new SqlDataAdapter(sqlCommand);

        dataTable = new DataTable();

        sqlDataAdapter.Fill(dataTable);

        // Get the mapping between the object property position and 
        // the SQL statment column position.
        Int32[] propertyPositions = objectQuery.GetPropertyPositions();

        // Create a column name to column position (ordinal) lookup.
        Dictionary<String, Int32> mapColumnNameToColumnPosition = new Dictionary<string, int>();

        // Populate the lookup.
        for (Int32 i = 0; i < propertyPositions.Length; ++i)
        {
            mapColumnNameToColumnPosition.Add(dataTable.Columns[propertyPositions[i]].ColumnName, i);

        }

        // Get the object's property information.
        PropertyInfo[] pi = query.GetType().GetGenericArguments()[0].GetProperties();

        // Iterate through the lookup and change the position of the datatable columns.
        // The order of the datatable columns will now correspond to the order of the object
        // properties.
        foreach (var map in mapColumnNameToColumnPosition)
        {
            // Change the column position.
            dataTable.Columns[map.Key].SetOrdinal(map.Value);

            // Change the column name.
            dataTable.Columns[map.Key].ColumnName = pi[map.Value].Name;

        }

        return dataTable;

    }
    catch (Exception ex)
    {
        // Something went wrong and we're going to raise an exception...we
        // might as well dispose of the datatable if it exists because it's
        // not going to be used.
        if (dataTable != null) dataTable.Dispose();

        throw new Exception("IQueryable to DataTable conversion error.", ex);

    }
    finally
    {
        // Do some cleanup on objects that are no longer needed.

        if (sqlDataAdapter != null) sqlDataAdapter.Dispose();

        if (sqlCommand != null) sqlCommand.Dispose();

        if (sqlConnection != null) sqlConnection.Dispose();

    }

}
于 2012-08-23T04:06:24.920 に答える