LINQ to Entities query to DataTable

c# datagridview datatable entity-framework linq

Question

I need to store the data returned from this LINQ to Entities query (below) into a DataTable so that I can use it as data source to a DataGridView, how can I do that?

In this case I'm using LINQ to Entities to query against an Entity Framework conceptual model, so db is a class that inherits from System.Data.Entity.DbContext.

using (TccContext db = new TccContext())
{
    var query = from vendedor in db.Vendedores.AsEnumerable()
                where vendedor.codigo == Convert.ToInt32(textBoxPesquisa.Text)
                select vendedor;
    // I'd like to do something like DataTable dt = query;
}

I've tried to do this (below), but it throws an exception during execution [1].

using (TccContext db = new TccContext())
{
    IEnumerable<DataRow> query = (IEnumerable<DataRow>)(from vendedor in db.Vendedores.AsEnumerable()
                                                        where vendedor.codigo == Convert.ToInt32(textBoxPesquisa.Text)
                                                        select vendedor);

    using (DataTable dt = query.CopyToDataTable<DataRow>())
    {
        this.dataGridViewProcura.Rows.Add(
            dt.Rows[0][0],  // Código
            dt.Rows[0][1],  // Nome
            dt.Rows[0][2]); // Venda Mensal
    }
}

[1]: Exception: InvalidCastException

Unable to cast object of type 'WhereEnumerableIterator`1[Projeto_TCC.Models.Vendedor]' to type 'System.Collections.Generic.IEnumerable`1[System.Data.DataRow]'.

Thanks in advance

1
5
8/25/2013 11:27:35 PM

Popular Answer

There is one important thing here, you are casting your Linq query to (IEnumerable<DataRow>) when you are selecting the vendedor, so I assume that vendedor is an instance of Vendedor, so your query will return an IEnumerable<Vendedor>

That should solve your problem, but also, can you try using the generated DataTable as the DataSource for your DataGridView? It would be something like this:

var query = (from vendedor in db.Vendedores.AsEnumerable()
                   where vendedor.codigo == Convert.ToInt32(textBoxPesquisa.Text)
                   select vendedor);
var dt = query.CopyToDataTable<Vendedor>();
this.dataGridViewProcura.DataSource = dt;

Hope I can help!

EDIT

As a side (and very personal) note, you could try using lambdas on your select, they look prettier :)

var pesquisa = Convert.ToInt32(textBoxPesquisa.Text);
var query = db.Vendedores.Where(vendedor => vendedor.codigo == pesquisa);

var dt = query.CopyToDataTable<Vendedor>();
this.dataGridViewProcura.DataSource = dt;

A lot cleaner, don't you think?

EDIT 2 I've just realized what you said on CopyToDataTable being for DataRow only, so last (admittedly not so clean) solution would be to mimic the logic on the helper?

public DataTable CopyGenericToDataTable<T>(this IEnumerable<T> items)
{
    var properties = typeof(T).GetProperties();
    var result = new DataTable();

    //Build the columns
    foreach ( var prop in properties ) {
        result.Columns.Add(prop.Name, prop.PropertyType);
    }

    //Fill the DataTable
    foreach( var item in items ){
        var row = result.NewRow();

        foreach ( var prop in properties ) {
            var itemValue = prop.GetValue(item, new object[] {});
            row[prop.Name] = itemValue;
        }

        result.Rows.Add(row);
    }

    return result;
}

Now, things to consider:

  • This solution will not work with complex properties
  • Customizing the resulting table might be a bit tricky

While this might solve the issue, I don't think this is a very good approach, but it could be the start of a decent idea :)

I hope I can help this time!

2
8/27/2013 10:58:22 PM


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