Sure, you can calculate the sum of a column value in a LINQ to SQL query using the Sum() method. The syntax is as follows:

C#

var sum = myTable.Sum(x => x.columnValue);

For example, if you have a table called products with a column called price, you could use the following LINQ to SQL query to calculate the sum of all product prices:

C#

var sum = products.Sum(x => x.price);

This would return the total sum of all product prices as an integer.

Here is an example of how to calculate the sum of a column value in a LINQ to SQL query in C#:

C#

using System;
using System.Data.Linq;

namespace LinqToSqlSum
{
    class Program
    {
        static void Main(string[] args)
        {
            // Create a LINQ to SQL query.
            var products = new LinqToSqlSumDataContext().Products;

            // Calculate the sum of all product prices.
            var sum = products.Sum(x => x.Price);

            // Display the sum.
            Console.WriteLine("The sum of all product prices is: {0}", sum);
        }
    }

    public class LinqToSqlSumDataContext : DbContext
    {
        public LinqToSqlSumDataContext()
        {
            Database.SetInitializer(new SqlServerInitializer());
        }

        public DbSet<Product> Products { get; set; }
    }

    public class Product
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int Price { get; set; }
    }
}

This code will first create a LINQ to SQL query for the products table. Then, it will calculate the sum of all product prices using the Sum() method. Finally, it will display the sum on the console.