Retrieving records from CRM 365 through c#

There are scenarios where you would want to retrieve records based on some condition.
To do that with the use of C#,below code can be used.

For example i have used account entity.

                QueryExpression query = new QueryExpression
               { EntityName = "account", ColumnSet = new ColumnSet("name", "accountid") };
       
                ConditionExpression condition1 = new ConditionExpression();
                condition1.AttributeName = "name";
                condition1.Operator = ConditionOperator.Equal;
                condition1.Values.Add("Your filter value");

                FilterExpression filter1 = new FilterExpression();
                filter1.Conditions.Add(condition1);

                query.Criteria.AddFilter(filter1);
       
                EntityCollection accountname = _service.RetrieveMultiple(query);

Other example with contact entity.

              QueryExpression query = new QueryExpression
              { EntityName = "contact", ColumnSet = new ColumnSet("firstname", "lastname",                                "emailaddress1", "contactid", "donotsendmm") };

              ConditionExpression condition1 = new ConditionExpression();
              condition1.AttributeName = "firstname";
              condition1.Operator = ConditionOperator.Equal;
              condition1.Values.Add(firstname);

              ConditionExpression condition2 = new ConditionExpression();
              condition2.AttributeName = "lastname";
              condition2.Operator = ConditionOperator.Equal;
              condition2.Values.Add(lastname);

              ConditionExpression condition3 = new ConditionExpression();
              condition3.AttributeName = "emailaddress1";
              condition3.Operator = ConditionOperator.Equal;
              condition3.Values.Add(email);

              FilterExpression filter1 = new FilterExpression();
              filter1.Conditions.Add(condition1);
              filter1.Conditions.Add(condition2);
              filter1.Conditions.Add(condition3);

              query.Criteria.AddFilter(filter1);

              EntityCollection accountname = _service.RetrieveMultiple(query);

Cheers!
Happy Development.