I have the following DbContext
and entity (.Net core 3.11 console program).
public partial class MyDbContext : DbContext
{
private readonly string _connectionString;
public MyDbContext(string connectionString) => _connectionString = connectionString;
public DbSet<MyEntity1> MyEntity1 { get; set; }
public DbSet<MyEntityX> MyEntityX { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) =>
optionsBuilder.UseSqlServer(_connectionString);
}
public class MyEntity1 { .... }
public class MyEntityX { .... }
I want to create a generic function with two type parameters for the entity class and column data type, and a string parameter for column name. The function will return
List<TColumn> F<TEntity, TColumn>(string colName)
{
var list = dbContext.Set<TEntity>()
.Select(x => x."colName?") // need to dynamic select the value of column
.ToList();
return list;
}
In this link ( https://www.strathweb.com/2018/01/easy-way-to-create-ac-lambda-expression-from-a-string-with-roslyn/ ), you can see how to create lambda expression from string. In there, he uses an example in Where(), but you should be able to create a Select() expression such as
var selectString = "x => x.colName";
var options = ScriptOptions.Default.AddReferences(typeof(TEntity).Assembly);
Func<TEntity, bool> selectExpression = await CSharpScript.EvaluateAsync<Func<TEntity, bool>>(selectString, options);
var selectedData = dbContext.Set<TEntity>().Select(selectExpression);
NOTE: you must always remember to use options to AddReferences() to your type.
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