SELECT t.TABLE_NAME As 'Table Name',
       Keys.COLUMN_NAME AS 'Primary Key'
FROM INFORMATION_SCHEMA.TABLES t
left outer join INFORMATION_SCHEMA.TABLE_CONSTRAINTS Constraints
         on  t.TABLE_NAME = Constraints.Table_name
         and t.Table_Schema = Constraints.Table_Schema
left outer join INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS Keys
         ON  Constraints.TABLE_NAME = Keys.TABLE_NAME
         and Constraints.CONSTRAINT_NAME = Keys.CONSTRAINT_NAME
         and Constraints.CONSTRAINT_TYPE = 'PRIMARY KEY'

SELECT T.TABLE_NAME As 'Table Name'
    ,       (
            Select K1.COLUMN_NAME
            From INFORMATION_SCHEMA.TABLE_CONSTRAINTS As C1
                Join INFORMATION_SCHEMA.KEY_COLUMN_USAGE As K1
                    On C1.TABLE_SCHEMA = K1.TABLE_SCHEMA
                        And C1.TABLE_NAME = K1.TABLE_NAME
                        And C1.CONSTRAINT_NAME = K1.CONSTRAINT_NAME
            Where C1.CONSTRAINT_TYPE = 'PRIMARY KEY'
                And T.TABLE_SCHEMA = C1.TABLE_SCHEMA
                And T.TABLE_NAME = C1.TABLE_NAME
            )As PrimaryKeyColumns
FROM INFORMATION_SCHEMA.TABLES As T

SELECT t.TABLE_NAME As 'Table Name',
       Keys.COLUMN_NAME AS 'Primary Key'
FROM INFORMATION_SCHEMA.TABLES t
left outer join INFORMATION_SCHEMA.TABLE_CONSTRAINTS Constraints
         on  t.TABLE_NAME = Constraints.Table_name
         and t.Table_Schema = Constraints.Table_Schema
         and Constraints.CONSTRAINT_TYPE = 'PRIMARY KEY'
left outer join INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS Keys
         ON  Constraints.TABLE_NAME = Keys.TABLE_NAME
         and Constraints.CONSTRAINT_NAME = Keys.CONSTRAINT_NAME

SELECT T.TABLE_NAME As 'Table Name'
    ,   Stuff(
            (
            Select ', ' + K1.COLUMN_NAME
            From INFORMATION_SCHEMA.TABLE_CONSTRAINTS As C1
                Join INFORMATION_SCHEMA.KEY_COLUMN_USAGE As K1
                    On C1.TABLE_SCHEMA = K1.TABLE_SCHEMA
                        And C1.TABLE_NAME = K1.TABLE_NAME
                        And C1.CONSTRAINT_NAME = K1.CONSTRAINT_NAME
            Where C1.CONSTRAINT_TYPE = 'PRIMARY KEY'
                And T.TABLE_SCHEMA = C1.TABLE_SCHEMA
                And T.TABLE_NAME = C1.TABLE_NAME
            For Xml Path(''), type
            ).value('.', 'nvarchar(max)')
            , 1, 2, '') As PrimaryKeyColumns
FROM INFORMATION_SCHEMA.TABLES As T

SELECT T.TABLE_NAME As 'Table Name'
    , Keys.COLUMN_NAME AS 'Primary Key'
FROM INFORMATION_SCHEMA.TABLES As T
    Left Join( INFORMATION_SCHEMA.TABLE_CONSTRAINTS Constraints
        Join INFORMATION_SCHEMA.KEY_COLUMN_USAGE As Keys
            On  Constraints.TABLE_SCHEMA = Keys.TABLE_SCHEMA
                And Constraints.TABLE_NAME = Keys.TABLE_NAME
                And Constraints.CONSTRAINT_NAME = Keys.CONSTRAINT_NAME
                And Constraints.CONSTRAINT_TYPE = 'PRIMARY KEY' )
        On T.TABLE_SCHEMA = Constraints.TABLE_SCHEMA
            And T.TABLE_NAME = Constraints.TABLE_NAME

static void Main(string[] args)
{
    Server server = new Server("serverName");
    Database db = server.Databases["DatabaseName"];

    string tableName = "TableName";

    Table table = db.Tables[tableName];

    if (table != null)
    {
        Console.WriteLine("Table:  {0}", tableName);
        if (table.Columns.Count > 0)
        {
            Console.WriteLine("  Primary Key Columns:");
            foreach (Column column in table.Columns)
            {
                if (column.InPrimaryKey)
                {
                    Console.WriteLine(string.Format("    {0}", column.Name));
                }
            }
        }
        else
        {
            Console.WriteLine("  No primary key.", tableName);
        }
    }
    Console.WriteLine("Press ENTER to exit...");
    Console.ReadLine();
}

select
  TABLE_SCHEMA,
  TABLE_NAME
from
  INFORMATION_SCHEMA.TABLES
where
  objectproperty(object_id(table_name),'TableHasPrimaryKey')=0
ORDER BY
  TABLE_NAME