Update Contact details to an Opportunity through Salesforce API - salesforce

Question

Need to create new relationship to Contact and Opportunity.
Trying to insert data to Case_Relation__c table for fields Opportunity__c SFDC_ContactID__c, etc. but it throws error:
Unable to create/update fields: Name. Please check the security settings of this field and verify that it is read/write for your profile or permission set.
API Code:
soqlQuery = "Select Case_Name__c,Case_Ranking__c,Company_Name__c,Contact_Role__c,Contact__c,Name,Opportunity__c,RUST_Case_Relationship_Legacy_ID__c,Relationship_Level__c,SFDC_ContactID__c FROM Case_Relation__c";
SalesForceProxy.QueryResult qrR = binding.query(soqlQuery);
done = false;
if (qrR.size > 0)
{
while (!done)
{
SalesForceProxy.sObject[] records = qrR.records;
for (int i = 0; i < records.Length; i++)
{
SalesForceProxy.Case_Relation__c con = (SalesForceProxy.Case_Relation__c)records[i];
oCmd.CreateParameter();
con.Opportunity__c = "006R0000008r0hdIAA";
con.SFDC_ContactID__c = "006R0000008r0hdIAA";
SFService.SalesForceProxy.sObject[] Case_Relation__c = new SalesForceProxy.sObject[1];
Case_Relation__c[0] = con;
if (qr.records != null)
{
try
{
SFService.SalesForceProxy.SaveResult[] saveResults = binding.create(Case_Relation__c);
for (int j = 0; j < saveResults.Length; j++)
{
if (saveResults[j].success)
{
}
else
{
foreach (SFService.SalesForceProxy.Error ex in saveResults[j].errors)
{
SendMail(ex.message);
TraceService(ex.message);
}
}
}
}
catch (Exception ex)
{
SendMail(ex.Message);
TraceService(ex.Message);
}
}
}
if (qrR.done)
{
done = true;
}
else
{
qrR = binding.queryMore(qrR.queryLocator);
}
}
}

Answer 1

check the field accessibility for every field in Case_Relation__c object