static Expression ConvertExpressionToType(Expression current, Type toType, MappingSchema mappingSchema)
{
var toConvertExpression = mappingSchema.GetConvertExpression(current.Type, toType, false, current.Type != toType);
if (toConvertExpression == null)
{
return(current);
}
current = InternalExtensions.ApplyLambdaToExpression(toConvertExpression, current);
return(current);
}
static Expression GetColumnReader(
IDataContext dataContext, MappingSchema mappingSchema, IDataReader dataReader, Type type, IValueConverter?converter, int idx, Expression dataReaderExpr, bool forceNullCheck)
{
var toType = type.ToNullableUnderlying();
Expression ex;
if (converter != null)
{
var expectedProvType = converter.FromProviderExpression.Parameters[0].Type;
ex = dataContext.GetReaderExpression(dataReader, idx, dataReaderExpr, expectedProvType);
}
else
{
ex = dataContext.GetReaderExpression(dataReader, idx, dataReaderExpr, toType);
}
if (ex.NodeType == ExpressionType.Lambda)
{
var l = (LambdaExpression)ex;
switch (l.Parameters.Count)
{
case 1: ex = l.GetBody(dataReaderExpr); break;
case 2: ex = l.GetBody(dataReaderExpr, ExpressionInstances.Int32(idx)); break;
}
}
if (converter != null)
{
// we have to prepare read expression to conversion
//
var expectedType = converter.FromProviderExpression.Parameters[0].Type;
if (converter.HandlesNulls)
{
ex = Condition(
Call(dataReaderExpr, Methods.ADONet.IsDBNull, ExpressionInstances.Int32Array(idx)),
Constant(mappingSchema.GetDefaultValue(expectedType), expectedType),
ex);
}
if (expectedType != ex.Type)
{
ex = ConvertExpressionToType(ex, expectedType, mappingSchema);
}
ex = InternalExtensions.ApplyLambdaToExpression(converter.FromProviderExpression, ex);
if (toType != ex.Type && toType.IsAssignableFrom(ex.Type))
{
ex = Convert(ex, toType);
}
}
else if (toType.IsEnum)
{
var mapType = ConvertBuilder.GetDefaultMappingFromEnumType(mappingSchema, toType) !;
if (mapType != ex.Type)
{
// Use only defined convert
var econv = mappingSchema.GetConvertExpression(ex.Type, type, false, false) ??
mappingSchema.GetConvertExpression(ex.Type, mapType, false) !;
ex = InternalExtensions.ApplyLambdaToExpression(econv, ex);
}
}
if (ex.Type != type)
{
ex = ConvertExpressionToType(ex, type, mappingSchema) !;
}
// Try to search postprocessing converter TType -> TType
//
ex = ConvertExpressionToType(ex, ex.Type, mappingSchema) !;
// Add check null expression.
// If converter handles nulls, do not provide IsNull check
// Note: some providers may return wrong IsDBNullAllowed, so we enforce null check in slow mode. E.g.:
// Microsoft.Data.SQLite
// Oracle (group by columns)
// MySql.Data and some other providers enforce null check in IsDBNullAllowed implementation
if (converter?.HandlesNulls != true &&
(forceNullCheck || (dataContext.IsDBNullAllowed(dataReader, idx) ?? true)))
{
ex = Condition(
Call(dataReaderExpr, Methods.ADONet.IsDBNull, ExpressionInstances.Int32Array(idx)),
Constant(mappingSchema.GetDefaultValue(type), type),
ex);
}
return(ex);
}