private void MapContainsExpression(MethodCallExpression expression)
{
DbExpression argExpression = GetDbExpressionForExpression(expression.Arguments[0]);
DbExpression dbExpression;
var collectionObjExp = expression.Object as ParameterExpression;
if (collectionObjExp != null)
{
// collectionObjExp is a parameter expression. This means the content of the collection is
// dynamic. DbInExpression only supports a fixed size list of constant values.
// So the only way to handle a dynamic collection is for us to create a single Equals expression
// with a DbParameterReference. Then when we intercept that parameter, we will see that it's
// for a collection and we will modify the SQL to change it from an "=" to an "in". The single
// Parameter Reference is set to the first value in the collection and the rest of the values
// are inserted into the SQL "in" clause.
string paramName = collectionObjExp.Name;
Type paramType = PrimitiveTypeForType(collectionObjExp.Type);
var param = CreateParameter(paramName, paramType);
dbExpression = argExpression.Equal(param);
}
else
{
var listExpression = expression.Object as ListInitExpression;
if (listExpression == null)
{
throw new NotSupportedException(string.Format("Unsupported object type used in Contains() - type = {0}", expression.Object.GetType().Name));
}
// This is a fixed size list that may contain parameter references or constant values.
// This can be handled using either a DbInExpression (if all are constants) or with
// a series of OR conditions.
// Find all of the constant & parameter expressions.
var constantExpressionList = listExpression.Initializers
.Select(i => i.Arguments.FirstOrDefault() as ConstantExpression)
.Where(c => (c != null) && (c.Value != null)) // null not supported - can only use DbConstant in "In" expression
.Select(c => CreateConstantExpression(c.Value))
.ToList();
constantExpressionList.AddRange(listExpression.Initializers
.Select(i => i.Arguments.FirstOrDefault() as UnaryExpression)
.Where(c => (c != null) && (c.Operand is ConstantExpression))
.Select(c => CreateConstantExpression(((ConstantExpression)c.Operand).Value)));
var parameterExpressionList = listExpression.Initializers
.Select(i => i.Arguments.FirstOrDefault() as ParameterExpression)
.Where(c => c != null)
.Select(c => CreateParameter(c.Name, c.Type))
.ToList();
if (constantExpressionList.Count + parameterExpressionList.Count != listExpression.Initializers.Count)
{
throw new NotSupportedException(string.Format("Unrecognized parameters in Contains list. Null parameters not supported."));
}
if (parameterExpressionList.Any())
{
// Have parameters so need to build a series of OR conditions so that we can include the
// DbParameterReferences. EF will optimize this into an "in" condition but with our
// DbParameterReferences preserved (which is not possible with a DbInExpression).
// The DbParameterReferences will be intercepted as any other parameter.
dbExpression = null;
var allExpressions = parameterExpressionList.Cast <DbExpression>().Union(constantExpressionList.Cast <DbExpression>());
foreach (var paramReference in allExpressions)
{
var equalsExpression = argExpression.Equal(paramReference);
if (dbExpression == null)
{
dbExpression = equalsExpression;
}
else
{
dbExpression = dbExpression.Or(equalsExpression);
}
}
}
else
{
// All values are constants so can use DbInExpression
dbExpression = argExpression.In(constantExpressionList);
}
}
MapExpressionToDbExpression(expression, dbExpression);
}