gistlib - implement a custom sql iqueryprovider in csharp

To implement a custom SQL IQueryProvider in C#, you can follow these steps:

Create a class that implements the IQueryProvider interface. This interface has two methods that you need to implement: CreateQuery and Execute.


main.cs
public class CustomQueryProvider : IQueryProvider
{
    public IQueryable CreateQuery(Expression expression)
    {
        throw new NotImplementedException();
    }

    public IQueryable<TElement> CreateQuery<TElement>(Expression expression)
    {
        throw new NotImplementedException();
    }

    public object Execute(Expression expression)
    {
        throw new NotImplementedException();
    }

    public TResult Execute<TResult>(Expression expression)
    {
        throw new NotImplementedException();
    }
}
527 chars
23 lines

Implement the CreateQuery method. This method should create a new IQueryable object based on the expression that is passed in as a parameter.


main.cs
public IQueryable CreateQuery(Expression expression)
{
    Type elementType = expression.Type.GetGenericArguments()[0];
    Type[] types = new[] { typeof(CustomQueryable<>).MakeGenericType(elementType) };
    object[] args = new[] { expression };
    return (IQueryable)Activator.CreateInstance(types[0], args);
}
314 chars
8 lines

Implement the CreateQuery<TElement> method. This method should create a new IQueryable object of the specified type based on the expression that is passed in as a parameter.


main.cs
public IQueryable<TElement> CreateQuery<TElement>(Expression expression)
{
    return new CustomQueryable<TElement>(expression);
}
131 chars
5 lines

Implement the Execute method. This method should execute the query that is represented by the expression that is passed in as a parameter and return the results as an object.


main.cs
public object Execute(Expression expression)
{
    throw new NotImplementedException();
}

public TResult Execute<TResult>(Expression expression)
{
    throw new NotImplementedException();
}
191 chars
10 lines

Create a custom IQueryable class. This class should implement the IQueryable interface and accept an expression as a parameter in its constructor. It should also implement the GetEnumerator method, which should return an enumerator that can be used to iterate over the results of the query.


main.cs
public class CustomQueryable<T> : IQueryable<T>
{
    private readonly Expression _expression;

    public CustomQueryable(Expression expression)
    {
        _expression = expression;
    }

    public IEnumerator<T> GetEnumerator()
    {
        throw new NotImplementedException();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }

    public Type ElementType => typeof(T);

    public Expression Expression => _expression;

    public IQueryProvider Provider => new CustomQueryProvider();
}
542 chars
26 lines

With these steps, you should be able to create a custom SQL IQueryProvider in C# that can be used to execute custom SQL queries.

implement a custom sql iqueryprovider in csharp

similar csharp code snippets

related categories