Issues with pushing huge data to azure search service index

Hi

we are trying to create search service in new portal and created index with some columns, while trying to insert huge data (more than 3 lakhs records) into search service index the search service index’s documents are not creating in index. Actually we tried to insert the data as JSON object and below are the approach we tried but it fails with below error. Please let us know if you have any alternative ways to push the huge data to azure search service index.

1.Converting list values to JSON objects

//Getting more than 3 lakhs records from table.

List<sampleModel> objTermModel = SearchIndex.GetDBContents();

Object pageListObj =new { value = objTermModel };

StringjssonValue=JsonConvert.SerializeObject(pageListObj);

Getting out of memory exception while assigning serialized JSON value into String variable.

We have tried created the indexes in batches , but it doesn't push the data to search service. Please suggest us an alternate solution or optimal way to handle such case.