Question

How to check if something exists in the DB

Jonathan Quendoz

12:23 Oct 07, 2021

Hi community,

When implementing a web service, I have a GET method with a parameter :

public int GetMethod(string name)

In this method, I did a query to get the age of the person in parameter :

var select = new Select(UserConnection)

.Column("Age")

.From("Contact")

.Where("Contact", "Name").IsEqual(Column.Parameter(name)) as Select;

Then I save the age into an int var :

var age = select.ExecuteScalar();

return age;

The problem is the following :

How can I check if the name of a contact in the method parameter exsists in the DB or not ?

Example :

if(name != exists) {

return 0;

} else {

return age;

}

Thanks a lot.

Best regards,

Jonathan

4 comments

Best reply

Cheng Gong

13:25 Oct 22, 2021

Hi Jonathan,

Usually you use dataReader to get the value from your select query. What you can do is:

bool hasRecord = false;
using (DBExecutor executor = UserConnection.EnsureDBConnection()) {
using (IDataReader dataReader = select.ExecuteReader(executor)) {
  while (dataReader.Read()) {
    hasRecord  = true;
  }
 }
}
if(hasrecord){
  return age
}else{
  return 0
}

Or you can just set the default value of the age =0. Therefore if the dataReader does not return any record, the default value age (0) will be returned.

regards,

Cheng Gong

Bogdan Lesyk

16:18 Oct 07, 2021

Hi Jonathan,

Please add the next using -

using Terrasoft.Common;

on the top of the page(if you didn't have this one).

Then in the part of the code when you are trying to retrieve the age:

if (name.IsNullOrEmpty())

{

return 0;

}

else

{

return age;

}

Best Regards,

Bogdan L.

Cheng Gong

13:25 Oct 22, 2021

Hi Jonathan,

Usually you use dataReader to get the value from your select query. What you can do is:

bool hasRecord = false;
using (DBExecutor executor = UserConnection.EnsureDBConnection()) {
using (IDataReader dataReader = select.ExecuteReader(executor)) {
  while (dataReader.Read()) {
    hasRecord  = true;
  }
 }
}
if(hasrecord){
  return age
}else{
  return 0
}

Or you can just set the default value of the age =0. Therefore if the dataReader does not return any record, the default value age (0) will be returned.

regards,

Cheng Gong

Jonathan Quendoz

09:45 Nov 02, 2021

Bogdan Lesyk,

Thanks for your answer. It helped a lot !

Jonathan Quendoz

09:46 Nov 02, 2021

Cheng Gong,

Your answer is really perfect ! Thanks a lot, i'll definitely save this snippet of code for my future implementations.

Regards,

Jonathan

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