First, this line:
sqlParams.Add(new SqlParameter() { ParameterName = "ConnectionTypeDesc", SqlDbType = SqlDbType.VarChar, Size = 100, Value = connectionTypeDesc });
has the wrong parameter name in it. It should be "@ConnectionTypeDesc".
Second, this type of error is easy to debug but you've made it difficult to do so because you're not putting anything into variables. You're mashing 3 statements into a single line of code. You really can't see which part of the line is throwing the exception. In your
return
statement, you've got 3 separate things going on.
To make your code easier to debug, put the result of the call to GetConnectionString() into a variable. Put the result of the call to GetInteger() into another variable then return this variable.
This is how you find out which part of that line of code is throwing the exception and it'll tell you where you need to look.