如何使用 Database.SqlQuery<> 读取 Int64 和 Int32 值

Question

I've wrote a function to check if specific ID exist in a table using schema name and name of table as input parameters.

Query which I created to execute on database will return -2 if it cannot find record with given ID and return its ID if item is found.

private long isThisNodeAlreadyInsertedInDatabaseByHeadquarter(
    string schemaName
    string tableName,
    string primaryNodeId,
    string primaryKeyFieldName){

    string targetTableName = $"{schemaName}.{tableName}";
    string sqlCommandString2 = $"select COALESCE(MAX({primaryKeyFieldName}),-2)" + " " + Environment.NewLine +
                             $"from {targetTableName}" + " " + Environment.NewLine +
                              "WHERE " + " " + Environment.NewLine +
                               $"{primaryKeyFieldName}={foundID}";
    //will return -2 if not found otherwise return its id
    DbRawSqlQuery<Int64> result2 = rawDbContext.Database.SqlQuery<Int64>(sqlCommandString2);
    long foundID = result2.Single();
    return foundID;
}

My Problem is that some primary keys in my database are of type Int and some are of type BigInt which are equivalent to Int32 and Int64 in C# respectively (or int and long respectively).

When I read primary keys of tables of type BigInt nothing wrong happens but when I want to read primary keys of table which are of type Int it causes exception:

{"The specified cast from a materialized 'System.Int32' type to the 'System.Int64' type is not valid."}

Although it is possible to store int in long variables, casting Int32 to Int64 in Database.SqlQuery causes this exception. I want to know are there any workarounds for this situation or I only have to read values using SqlDataReader.ExecuteReader ?

Answer 1

Convert PK to BIGINT in query and read as Int64 :

"select CONVERT(BIGINT,COALESCE(MAX({primaryKeyFieldName}),-2))"

Also, you can replace COALESCE with ISNULL function:

"select CONVERT(BIGINT,ISNULL(MAX({primaryKeyFieldName}),-2))"