Question

how can I pass value from selected field (LINQ) to textbox in winforms?

If single fields, I just do like this

   var result = from row in dtValueBranch.AsEnumerable()
                         where row.Field<int>("branchID") == idBranch
                         select row.Field<string>("branchName");

        StringBuilder sb = new StringBuilder();

        foreach (string s in result)
        {
            sb.Append(s + Environment.NewLine);
        }

        tbBranch.Text = sb.ToString();

So this is the code LINQ to many fields

    var result = from row in dtValueBranch.AsEnumerable()
                 where row.Field<int>("branchID") == idBranch
                 select new
                 {
                      BranchName = row["branchName"].ToString(),
                      branchTel = row["branchTel1"].ToString(),
                      // And many more fields

                 };

How can I to implement each fields to each textbox?

Answer 1

Keeping in mind that your result query may have multiple rows, your question appears to be focused on how to access the fields of one row. You can do that like this:

var row = result.First();  // select first row of results

textbox1.Value = row.BranchName;
textbox2.Value = row.branchTel;
// etc..

The select new syntax in your query creates an anonymous type in the result enumeration. You can’t refer to that type by name, but you can create local variables (like row) if you use the var declaration style and let the compiler do type inferencing.

If you want to cram all the values of one field across all rows into into one textbox (as in your first code sample), you can do something like this:

    StringBuilder sbBranch = new StringBuilder();
    StringBuilder sbBranchTel = new StringBuilder();
    // etc

    foreach (var row in result)
    {
        sbBranch.Append(row.BranchName);
        sbBranch.Append(Environment.NewLine);
        sbBranchTel.Append(row.branchTel);
        sbBranchTel.Append(Environment.NewLine);
        // etc
    }

    tbBranch.Text = sbBranch.ToString();
    tbBranchTel.Text = sbBranchTel.ToString();
    // etc

However, if you’re wanting to display multiple rows of multiple fields of data, you might want to look at using a data grid control instead of a herd of textboxes. You’ll save yourself a lot of effort, and your users will probably thank you too.