public static DataMapper GetMapper(IDbCommand command, IDataReader reader)
{
var cacheKey = new DataMapperCache.Key(command, typeof(BlazerDynamicObject));
if (DataMapperCache.TryGet(cacheKey, out DataMapper cachedMapper))
{
return(cachedMapper);
}
var columns = new string[reader.FieldCount];
for (int i = 0; i < reader.FieldCount; i++)
{
columns[i] = reader.GetName(i);
}
DataMapper lambda = (record) =>
{
var values = new object[record.FieldCount];
var blzDynamic = new BlazerDynamicObject(values.Length);
record.GetValues(values);
for (int i = 0; i < values.Length; i++)
{
var value = values[i];
blzDynamic.Set(columns[i], value == DBNull.Value ? null : value);
}
return(blzDynamic);
};
DataMapperCache.Add(cacheKey, lambda);
return(lambda);
}
public static DataMapper GetMapper <T>(IDbCommand command, IDataReader reader) where T : new()
{
var entityType = typeof(T);
var cacheKey = new DataMapperCache.Key(command, entityType);
if (DataMapperCache.TryGet(cacheKey, out DataMapper cachedMapper))
{
return(cachedMapper);
}
var dataRecordType = typeof(IDataRecord);
var dataRecordParamExpr = Expression.Parameter(dataRecordType, "record");
var dataRecordIsDbNullMethod = dataRecordType.GetMethod(nameof(IDataRecord.IsDBNull), new[] { typeof(int) });
var mapperBodyExpressions = new List <Expression>();
var returnLabelExpr = Expression.Label(entityType);
// T entity;
var entityVarExpr = Expression.Variable(entityType, "entity");
// entity = new T();
var entityNewExpr = Expression.Assign(
entityVarExpr,
Expression.New(entityType));
mapperBodyExpressions.Add(entityNewExpr);
for (int i = 0; i < reader.FieldCount; i++)
{
var entityField = GetEntityField(entityType, reader.GetName(i));
if (entityField == null)
{
continue;
}
Type entityFieldType = null;
Expression entityFieldExpr = null;
if (entityField is PropertyInfo propInfo)
{
entityFieldType = propInfo.PropertyType;
entityFieldExpr = Expression.Property(entityVarExpr, propInfo);
}
else if (entityField is FieldInfo fieldInfo)
{
entityFieldType = fieldInfo.FieldType;
entityFieldExpr = Expression.Field(entityVarExpr, fieldInfo);
}
var ctx = new Context()
{
EntityFieldType = entityFieldType,
EntityFieldExpr = entityFieldExpr,
DataRecordParameterExpr = dataRecordParamExpr,
DataRecordIsDbNullMethod = dataRecordIsDbNullMethod,
FieldIndex = i
};
mapperBodyExpressions.Add(GetFieldMapperExpression(ctx));
}
// return entity;
var entityReturnExpr = Expression.Return(returnLabelExpr, entityVarExpr);
mapperBodyExpressions.Add(entityReturnExpr);
// default return value
var defaultReturnExpr = Expression.Label(returnLabelExpr, Expression.Constant(null, entityType));
mapperBodyExpressions.Add(defaultReturnExpr);
var lambdaBodyExpr = Expression.Block(
new[] { entityVarExpr },
mapperBodyExpressions);
var lambdaExpr = Expression.Lambda <DataMapper>(lambdaBodyExpr, dataRecordParamExpr);
var lambda = lambdaExpr.Compile();
DataMapperCache.Add(cacheKey, lambda);
return(lambda);
}
