Conversion from string to int in LINQ to SQL query

Question

In Sql i have a string column which stores time value in mm:ss format. While writing LINQ to SQL query in C# I need to add that time value in date value which is another sql column.

 

To do that i will have to write

DBFunction.AddHours(DateColumn,(double)TimeColumn.Substring(0,2)

but it gives complie time error.

 

I tried  

 

DBFunction.AddHours(DateColumn,Convert.ToDouble(TimeColumn.Substring(0,2)) but it gives run time error as it is non supported method.

 

What is the solution if anyone can help.