public void TestStringToNullable()
{
Assert.AreEqual(typeof(string), NullableUtils.ToNullable(typeof(string)));
}
public void TestNullableIntToNullable()
{
Assert.AreEqual(typeof(int?), NullableUtils.ToNullable(typeof(int?)));
}
public void TestStructToNullable()
{
Assert.AreEqual(typeof(TestStruct?), NullableUtils.ToNullable(typeof(TestStruct)));
}
private void VisitFirst(FunctionCall functionCall)
{
if (functionCall.Parameters.Count != 1 && functionCall.Parameters.Count != 2)
{
throw new SqlErrorException("'first' must contain either one or two parameters");
}
if (!(functionCall.Parameters[0] is ScalarExpression scalarExpression))
{
throw new SqlErrorException("'first' first parameter must be a scalar expression");
}
scalarExpression.Accept(this);
var column = PopStack();
//Check that is in an array (IEnumerable)
if (!ArrayUtils.IsArray(column.Type))
{
throw new SqlErrorException("'first' first parameter must be an array/list.");
}
//Get the type that the array contains
var elementType = ArrayUtils.GetArrayElementType(column.Type);
Expression lambda = null;
if (functionCall.Parameters.Count == 2)
{
if (!(functionCall.Parameters[1] is SqlParser.Expressions.LambdaExpression lambdaExpression))
{
throw new SqlErrorException("'first' second parameter must be a lambda expression");
}
if (lambdaExpression.Parameters.Count != 1)
{
throw new SqlErrorException("'first' lambda expression can only have one input parameter");
}
//Add the type to the lambda settings in the base visitor
if (_lambdaParameters == null)
{
_lambdaParameters = new Stack <Dictionary <string, ParameterExpression> >();
}
_lambdaParameters.Push(new Dictionary <string, ParameterExpression>()
{
{ lambdaExpression.Parameters.First(), Expression.Parameter(elementType) }
});
//Visit the lambda expression
lambdaExpression.Accept(this);
lambda = PopStack();
if (!(lambda is System.Linq.Expressions.LambdaExpression expr) || expr.ReturnType != typeof(bool))
{
throw new SqlErrorException("Lambda expression in 'first' must return a boolean.");
}
}
var whereCall = ArrayFunctionUtils.CallFirstOrDefault(elementType, column, lambda);
var nullableType = NullableUtils.ToNullable(whereCall.Type);
if (nullableType != whereCall.Type)
{
whereCall = Expression.Convert(whereCall, nullableType);
}
var nullCheck = Expression.Condition(Expression.Equal(column, Expression.Constant(null, column.Type)), Expression.Constant(null, nullableType), whereCall);
AddExpressionToStack(nullCheck);
}