CODEWITHSUNDEEP
c#sql
Rob
Rob

Reputation: 2472

How to use variables declared within an if statement?

Last time I had a similar question, but we figured out if initialize and set a value for the variable before the logic statement then I can use the value that was generated within the logic statement.

This time, I want to call one of two method overloads depending on if the connection string is empty or not. Like so.

if (ConnectionString != "") // if there is something in the config file work with it
{
  SqlConnection dataConnection = new SqlConnection(ConnectionString);
}
else
{
  SqlConnection dataConnection = new SqlConnection();
}

try {
  // ...

The problem is that anything in the try block fails because it does not know about the dataConnection.

How can do I do this in a way to make it work?

Upvotes: 1

Views: 1151

Answers (5)

CD..
CD..

Reputation: 74166

You can do it like this:

SqlConnection dataConnection = !string.IsNullOrEmpty(ConnectionString)
    ? new SqlConnection(ConnectionString) :  new SqlConnection();

Or:

SqlConnection dataConnection;
if (string.IsNullOrEmpty(ConnectionString))
{
    dataConnection = new SqlConnection(ConnectionString);
}
else
{
    dataConnection = new SqlConnection();
}

Upvotes: 5

Marc Gravell
Marc Gravell

Reputation: 1063338

Declare it (uninitialized) outside:

SqlConnection conn;
if(string.IsNullOrEmpty(connectionString)) {
    conn = new SqlConnection();
} else {
    conn = new SqlConnection(connectionString);
}

If the logic is simple, a conditional is possible too:

SqlConnection conn = string.IsNullOrEmpty(connectionString)
     ? new SqlConnection() : new SqlConnection(connectionString);

The latter is much easier to use with a using block, as it can be done inline.

Upvotes: 3

Muhammad Al-Own
Muhammad Al-Own

Reputation: 237

You can declare the variable with null value out side the if statment and then use it inside the if statment and when you need to use it check if it's not null

SqlConnection dataConnection = null;
if (ConnectionString != "") // if there is something in the config file work with it
{
    dataConnection = new SqlConnection(ConnectionString);
}
else
{
    dataConnection = new SqlConnection();
}
try
{
    if(dataConnection != null)
        DoWhatYouWant();
}

Upvotes: 1

om-nom-nom
om-nom-nom

Reputation: 62835

I think you should define connection before if statements

 SqlConnection dataConnection = null;
    if (ConnectionString != "") // if there is something in the config file work with it
        {
            dataConnection = new SqlConnection(ConnectionString);
        }
        else
        {
            dataConnection = new SqlConnection();
        }
        try
        {

Upvotes: 1

LarsTech
LarsTech

Reputation: 81645

You have to have the variable outside the if block:

SqlConnection dataConnection;
if (ConnectionString != "") // if there is something in the config file work with it
{
  dataConnection = new SqlConnection(ConnectionString);
}
else
{
  dataConnection = new SqlConnection();
}

Upvotes: 1

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