/// <summary>
 /// Set page variables. Use last enter values as defaults. Otherwise use default values.
 /// </summary>
 private void SetPageVariables()
 {
     // CommonItems.stringNameMaterial not used to calculate results.
     CommonItems.stringNameMaterial = LibMPC.DataStoreStringToString(mainPage.applicationDataContainer, CommonItems.ds_StringNameMaterial);
     if (CommonItems.stringNameMaterial.Length.Equals(0))
     {
         TboxBeamPropertiesNameMaterial.Text = string.Empty;   // Set default value.
     }
     else
     {
         TboxBeamPropertiesNameMaterial.Text = CommonItems.stringNameMaterial;      // Use last value entered.
     }
     CommonItems.doubleYoungsModulus = LibMPC.DataStoreStringToDouble(mainPage.applicationDataContainer, CommonItems.ds_DoubleYoungsModulus);
     if (CommonItems.doubleYoungsModulus.Equals(0d))
     {
         CommonItems.boolEnteredYoungsModulus = false;
         TboxBeamPropertiesYoungsModulus.Text = string.Empty;
     }
     else
     {
         CommonItems.boolEnteredYoungsModulus = true;
         TboxBeamPropertiesYoungsModulus.Text = CommonItems.doubleYoungsModulus.ToString(LibNum.fpNumericFormatSeparator);     // Use last value entered.
     }
     CommonItems.doublePoissonsRatio = LibMPC.DataStoreStringToDouble(mainPage.applicationDataContainer, CommonItems.ds_DoublePoissonsRatio);
     if (CommonItems.doublePoissonsRatio.Equals(0d))
     {
         CommonItems.boolEnteredPoissonsRatio = false;
         TboxBeamPropertiesPoissonsRatio.Text = string.Empty;
     }
     else
     {
         CommonItems.boolEnteredPoissonsRatio = true;
         TboxBeamPropertiesPoissonsRatio.Text = CommonItems.doublePoissonsRatio.ToString(LibNum.fpNumericFormatNone);     // Use last value entered.
     }
     // CommonItems.stringNameCrossSection not used to calculate results.
     CommonItems.stringNameCrossSection = LibMPC.DataStoreStringToString(mainPage.applicationDataContainer, CommonItems.ds_StringNameCrossSection);
     if (CommonItems.stringNameCrossSection.Length.Equals(0))
     {
         TboxBeamPropertiesNameCrossSection.Text = string.Empty;   // Set default value.
     }
     else
     {
         TboxBeamPropertiesNameCrossSection.Text = CommonItems.stringNameCrossSection;      // Use last value entered.
     }
     CommonItems.doubleInertia = LibMPC.DataStoreStringToDouble(mainPage.applicationDataContainer, CommonItems.ds_DoubleInertia);
     if (CommonItems.doubleInertia.Equals(0d))
     {
         CommonItems.boolEnteredInertia = false;
         TboxBeamPropertiesInertia.Text = string.Empty;     // Set default value.
     }
     else
     {
         CommonItems.boolEnteredInertia = true;
         TboxBeamPropertiesInertia.Text = CommonItems.doubleInertia.ToString(LibNum.fpNumericFormatNone);   // Use last value entered.
     }
     CommonItems.doubleBeamLength = LibMPC.DataStoreStringToDouble(mainPage.applicationDataContainer, CommonItems.ds_DoubleBeamLength);
     if (CommonItems.doubleBeamLength.Equals(0d))
     {
         TboxBeamPropertiesLength.Text = string.Empty;      // Set default value.
     }
     else
     {
         TboxBeamPropertiesLength.Text = $"{CommonItems.doubleBeamLength:G}";   // Use last value entered.
     }
     CheckBeamPropertyInputValues();
 }