Do not clear the columns to clear the grid.
Set the datasource to null instead
dgvSolutions.DataSource=null;
To update your gridview,
make required changes / load a new DataTable and set it as the datasource
dgvSolution.AutoGenerateColumns = true;
dgvSolution.DataSource = dt;
If you do not wish columns to be auto-generated, then you must add columns manually & set each column's DataPropertyName to the DataTable's Field Name & then assign the source. (You can also add columns & set DataPropertyName in the designer)