protected virtual Expression VisitDeclaration(DbDeclaration decl)
{
ReadOnlyCollection <DbVariableDeclaration> variables = VisitVariableDeclarations(decl.Variables);
DbSelectExpression source = (DbSelectExpression)Visit(decl.Source);
return(UpdateDeclaration(decl, variables, source));
}
protected DbDeclaration UpdateDeclaration(DbDeclaration decl,
IEnumerable <DbVariableDeclaration> variables, DbSelectExpression source)
{
if (variables != decl.Variables || source != decl.Source)
{
return(new DbDeclaration(variables, source));
}
return(decl);
}
protected override Expression VisitDeclaration(DbDeclaration decl)
{
if (decl.Source != null)
{
// make query that returns all these declared values as an object[]
var projection = new DbProjectionExpression(
decl.Source,
Expression.NewArrayInit(
typeof(object),
decl.Variables.Select(v => v.Expression.Type.IsValueType
? Expression.Convert(v.Expression, typeof(object))
: v.Expression).ToArray()
),
Aggregator.Aggregate(typeof(object[]), typeof(IEnumerable <object[]>))
);
// create execution variable to hold the array of declared variables
var vars = Expression.Parameter(typeof(object[]), "vars");
this.variables.Add(vars);
this.initializers.Add(Expression.Constant(null, typeof(object[])));
// create subsitution for each variable (so it will find the variable value in the new vars array)
for (int i = 0, n = decl.Variables.Count; i < n; i++)
{
var v = decl.Variables[i];
DbNamedValueExpression nv = new DbNamedValueExpression(
v.Name, v.DbType,
Expression.Convert(Expression.ArrayIndex(vars, Expression.Constant(i)), v.Expression.Type)
);
this.variableMap.Add(v.Name, nv);
}
// make sure the execution of the select stuffs the results into the new vars array
return(MakeAssign(vars, this.Visit(projection)));
}
// probably bad if we get here since we must not allow mulitple commands
throw new InvalidOperationException("Declaration query not allowed for this langauge");
}
protected DbDeclaration UpdateDeclaration(DbDeclaration decl,
IEnumerable<DbVariableDeclaration> variables, DbSelectExpression source)
{
if (variables != decl.Variables || source != decl.Source)
return new DbDeclaration(variables, source);
return decl;
}
protected virtual Expression VisitDeclaration(DbDeclaration decl)
{
ReadOnlyCollection<DbVariableDeclaration> variables = VisitVariableDeclarations(decl.Variables);
DbSelectExpression source = (DbSelectExpression)Visit(decl.Source);
return UpdateDeclaration(decl, variables, source);
}
protected override Expression VisitDeclaration(DbDeclaration decl)
{
throw new NotSupportedException();
}