/// <summary>
/// Helper method for <see cref="TransformIntersectOrExcept(DbExpression left, DbExpression right, DbExpressionKind expressionKind, IList<DbPropertyExpression> sortExpressionsOverLeft, string sortExpressionsBindingVariableName)"/>
/// Creates a <see cref="DbProjectExpression"/> over the given inputBinding that projects out the given flattenedProperties.
/// and updates the flattenedProperties to be over the newly created project.
/// </summary>
/// <param name="inputBinding"></param>
/// <param name="flattenedProperties"></param>
/// <returns>An <see cref="DbExpressionBinding"/> over the newly created <see cref="DbProjectExpression"/></returns>
private static DbExpressionBinding CapWithProject(DbExpressionBinding inputBinding, IList<DbPropertyExpression> flattenedProperties)
{
var projectColumns = new List<KeyValuePair<string, DbExpression>>(flattenedProperties.Count);
//List of all the columnNames used in the projection.
var columnNames = new Dictionary<string, int>(flattenedProperties.Count);
foreach (var pe in flattenedProperties)
{
//There may be conflicting property names, thus we may need to rename.
var name = pe.Property.Name;
int i;
if (columnNames.TryGetValue(name, out i))
{
string newName;
do
{
++i;
newName = name + i.ToString(CultureInfo.InvariantCulture);
}
while (columnNames.ContainsKey(newName));
columnNames[name] = i;
name = newName;
}
// Add this column name to list of known names so that there are no subsequent
// collisions
columnNames[name] = 0;
projectColumns.Add(new KeyValuePair<string, DbExpression>(name, pe));
}
//Build the project
DbExpression rowExpr = DbExpressionBuilder.NewRow(projectColumns);
var projectExpression = inputBinding.Project(rowExpr);
//Create the new inputBinding
var resultBinding = projectExpression.Bind();
//Create the list of flattenedProperties over the new project
flattenedProperties.Clear();
var rowExprType = (RowType)rowExpr.ResultType.EdmType;
foreach (var column in projectColumns)
{
var prop = rowExprType.Properties[column.Key];
flattenedProperties.Add(resultBinding.Variable.Property(prop));
}
return resultBinding;
}
internal DbExpression Project(DbExpressionBinding input, DbExpression projection)
{
var lifter = GetLifter(input.Expression);
return lifter.Project(input.Project(projection));
}
